Honestly friend, this is a really good analysis. You've managed to sum up about the last thirty years of thought in ~ 5 paragraphs. This is some really incredible writing and thinking.

I can give you a bit of what I know but I'm approximately five professional degrees short of being remotely qualified.

1.) You're mostly correct here only there are not separate treaties for each band. The Canadian government recognizes 73 treaties that date from 1701 - 1921. These treaties run the gamut from "Please don't kill us" to "Please help us kill the French" to "Okay, now give us all your land." When people talk treaties, they're mostly talking about numbered treaties - I was born on Treaty 6 lands and I live and work on Treaty 4 lands.

These treaties are quite complicated and have a number of complicated legal arguments associated with them. Canada has violated these treaties in really messed up ways. For example, most treaties called for Indigenous children to receive an education on reserve. That didn't happen and instead, we put them in concentration camps for kids.

Because the treaties have been largely violated, there's a lot of debate amongst Indigenous people. Some think it would be good enough if Canada would just follow what has been signed. Others take on a more abolish them approach. And still others take on a renegotiate them approach. All three of these are complicated because treaties are foundational agreements for land and resource use. I don't know enough to provide more information, but I can share this paper:

http://www.cba.org/cba/cle/PDF/ABOR11_Craft_Paper.pdf

Incidentally, Aimee Craft is a very good writer - she currently teaches law at the University of Ottawa and has published some very interesting papers. If you're as into this subject as you seem, I bet you would have a lot of fun going through some of the stuff on her UO page:

https://commonlaw.uottawa.ca/en/people/craft-aimee

2.) This is where stuff gets interesting. There are groups that try to bring bands together and other groups that try to keep them apart. As you mention, they have dramatically different cultures, languages and territories. On a national level, we have a group called the Assembly of First Nations:

https://www.afn.ca/Home/

Provinces also have assemblies. In Saskatchewan, we call it FSIN (Federation of Sovereign Indian Nations).

https://www.fsin.ca/

As you go through, learn more about the various groups and their ideas, I think you'll see lots of areas that pertain to all Indigenous people and others that are more niche. Indigenous politics are really interesting!!

3.) This one is a perfect example of #2. It's a long story with a lot of crazy twists and turns but the short answer is that we didn't include much about Indigenous rights and privileges while we were drafting our Constitution. It led to a really crazy (and remarkably rare) example of Canadian national unity in which virtually all the bands agreed that that was a bullshit constitution so they demonstrated en masse. The Prime Minister at the time was our current Prime Minister's father.

The actual section shouldn't cause too much friction but this is Canada and whenever there is any kind of constitutional question that could have to go to the provinces, everything goes completely to shit. So while the wording is mundane, I'm pretty sure that it will turn into another constitutional crisis just like we have every single time we try to change something.

Basically though, section 35 affirms current rights but adds in the provision for new rights to be added through land claims or other processes. So it doesn't box Indigenous affairs in too much while still acknowledging that Canada is founded upon treaties.

It starts to get a little more interesting when you start looking into Supreme Court challenges. This is R v. Sparrow:

https://www.canlii.org/en/ca/scc/doc/1990/1990canlii104/1990...

Check out the list of respondents and consider reading the ruling as well as this case which points out some holes between Federal and provincial jurisdiction:

https://www.canlii.org/en/ab/abpc/doc/2007/2007abpc278/2007a...