For the OP, I see some good news:

Generally there is better advice!

=== Startup Big Point

Here is a big, huge, gigantic point about
doing a startup and owning 100% of it: In
broad terms, that's the American way!

Or, it's obvious; just look: All across
the US, east to west, north to south, from
an isolated house in the woods to a
crossroads up to the largest cities, sole,
solo entrepreneurs start and run
successful businesses. No biggie. No
tech. No MBA. No venture funding. No
team of co-founders. By the millions --
wrong, by the 10s of millions. If that
was so difficult to do, then there
wouldn't be tens of millions of people
doing it.

=== US Mainline Business

What do they do?

Mow grass -- the ones on my street show up
with $100+ K of capital equipment counting
the truck, the trailer, the mowers, etc.

Note: Now $100 K will pay for one heck of
a powerful Web server farm; if you can
keep that farm busy, then just at standard
ad rates you have nearly a license to
print money. Or, for computing, $100 K in
capital equipment is now a LOT.

Do auto body repair.

Do other auto repair.

Sell car tires.

Add asphalt to driveways.

Do landscaping, architecture to grass mowing,
for good customers, e.g., any company with
nice grounds.

A dentist.

A CPA.

A pizza carryout.

A Chinese food carryout.

An Italian red sauce restaurant.

A manufacturer's representative.

A local wholesale plumbing, electrical,
building materials supplier.

A wide range of what can be called big
truck, little truck businesses -- buy
stuff delivered in a big truck and sell it
out of a little truck.

Run several fast food restaurants, gas
stations with convenience stores, etc.

And on and on.

Generally these businesses have one of the
most powerful advantages in all of
business -- a strong barrier to entry.
That barrier is, and may I have the
envelope, please [drum roll],
geographical, that is, the businesses are
not in competition with anyone more than
100 miles away. In particular they are
100% immune to competition from China. If
they are in Tennessee, then they have no
competition with anyone in NYS or CA. Etc.
So, if they can do comparatively well in a
radius of 100 miles, then they can do well
for their career.

A huge fraction of the people who pay full
tuition for their children at private
universities did not take venture capital,
did not have co-founders, didn't get an
MBA or a STEM field college degree, were
nearly never an employee, and were not
close to any of the scenarios in the OP.

Okay, that, my friends, is American
Business 101 Facts of Life. That's the
overwhelmingly popular version of US
business and, indeed, US careers. Nothing
else even comes close. And the OP is far
away from that.

So, take that US business 101 and, with
computing, try to do more -- the computing
should be an advantage.

=== Being an Executive

Okay, briefly, for being an executive: No
security. None. Zip, zilch, zero. No
matter what. Instead are an at will
employee that at any time can be fired for
any reason or no reason. Biggie reasons
for getting fired: (A) As in the OP,
office politics. E.g., there's gossip
(you get accused, tried, convicted, and
fired all while knowing nothing about it).
(B) The company does poorly. (C) The
company does fairly well but gets bought
out by another company. (D) The owner has
a son and wants to give him your job.
Etc. The crucial point is, you don't own
the business.

Just as an executive, your skills,
alliances, knowledge of your current job,
etc. anywhere else with a dime usually
won't cover a 10 cent cup of coffee.

Is there a way? Okay, be in sales and
have a nice list of your accounts that do
well. You don't really want to be the
sales manager, just a good sales guy. If
your employer goes out of business, gets
bought out, etc., then take your customer
list to whatever company in the industry
wants to server your customer list. Be
sure the industry will be solid even if
your employer might not be.

There's just no magic to being an
executive. And there's nearly no power;
instead your job is to get along, go
along, and hope nothing bad happens. If
you sponsor a new project and it fails,
then you have a black mark on your record,
and everyone else has an excuse to gang up
to fire you. If the project is
successful, then you have jealous enemies
all the way to and including the BoD.

Part of this is the fact that currently
the US economy has about 94 million people
out of the labor force. So, mostly,
there's no shortage.

Currently it's too common for Mr. Big CEO
to wake up, have a bad day, look at his
budget and organization, draw a big X, and
say "Off with their heads." In this way
big, famous companies have suddenly fired
dozens, hundreds, thousands, tens of
thousands of people. E.g., at one time,
as computing was roaring ahead, IBM
suddenly went from 407,000 employees down
to 209,000. They cleaned out rush hour
traffic over big parts of NY, CT, and NJ.

Another time, at IBM Research, a group of
about 100 people got into serious
political trouble, and when the dust
settled a lot of managers were demoted or
fired and a about half of the rest, about
have high-end Ph.D. holders, were fired.
It was all about work-place politics,
cliques fighting each other, etc.

Sure, decades ago lots of people could
join a company and work until a nice
retirement. Things changed slowly. E.g.,
could work for Sears for decades and
retire. Sears? It's about to go belly
up, totally. No more; that's rarely the
case now. If you really want that, then:
(A) Work for a company, e.g., a public
utility, where the employees have a strong
union and join the union. E.g., at one
time could do that with the Bell System.
Alas, even Ma Bell didn't last. A local
water company might be better. Be careful
about a local electric utility since that
industry might change a lot before you get
to retire. (B) Work for government,
local, state, or Federal. Remember,
though, even working for government have
to be careful about the slot. E.g., don't
be a civilian Civil Service employee for
the US military: Then some military
officer is running the place; they likely
have their job changed each two years or
so; so a new guy comes in and quickly
doesn't like you or your job, and you are
OUT. So, each two years you have to sell
yourself to another person you never met
before. That person can make a big
mistake firing you, but, then, you are
still fired. So, for a 40 year career,
you have to sell yourself to 20 people you
never met before, and you have to be 100%
successful in all 20 attempts. That's not
good job security. (C) Work for, say,
some very solid, stable financial
institution, maybe The Ford Foundation.

Officer in the US military? Every now and
then you are up for promotion, and if you
get passed over three times or some such,
then you are out. So, as time goes on,
the many lower level officers become many
fewer upper level officers. It's not at
all clear which lower level officers will
leave; it is totally clear that nearly all
of them will.

Net, it's better to be a non-commissioned
officer, e.g., a sergeant where you can
keep your job. Even if you get 4 stars,
like General Mattis, you can be out
because someone up there didn't like you.

Some private companies have personnel
policies similar to the military for their
officers: They hire lots of people in
their 20s, and by age 35 they are in
management or out the door. It's not at
all clear who will be out the door, but
it's totally clear that nearly all of them
will be. A lot of those people would be
better off in their 20s starting and
growing a grass mowing service, quite
literally: There's a good geographical
barrier to entry, and the grass will keep
growing. Commonly in the US, a Ph.D. in
electronic engineering will have a better
long term career as a licensed
electrician. No joke.

I know a guy, bright enough, who got a
Master's in environmental engineering.
His real career was as a plumber and
installer of home heating systems.

=== Being a Founder

What the OP says about being a founder is
quite narrow.

I have a high school friend. His father
was selling beer for a small brewery. The
brewery went out of business, but he knew
a lot of people in the beer business. He
went to the NW corner of his state,
arranged to distribute about six brands of
beer (right, the beer came to his
warehouse on a railroad siding via
railroad freight car) and sold out of
little trucks. Somehow people still like
beer! He passed the business down to his
son. People still like beer! Good
business. Darned good business.

If want to go into computing, then be sure
you have an even better business than
selling beer.

The OP wants to say that the business idea
in computing is not very important. IMHO,
that's mostly nonsense.

Sure, if want only routine technology,
then the OP comments about employees,
teams, etc. are important. But a business
with only routine technology tends to have
a darned small barrier to entry. Sure,
one of the best barriers to entry was
virality from a social network with a
strong network effect, but that's path
seems to be about saturated.

Again, there are 94 million people out of
the labor force. So, if you want a job as
founder of a successful business, then,
IMHO, need to do something new and
powerful with a good barrier to entry.
Basically you have to plow new ground in
US business, have to do something those 94
million don't know how to do.