Time for a longer reply:

> Are there any recommended resources (Books/blogs/courses/etc.) I should look into?
Million dollar consultant is a ridiculous book, but shocked me out of being too far on the other end of the spectrum about some issues. You will walk away thinking "if someone like the author can make it big (maybe with a bit of luck), I can certainly make it small, at least"
A more reasonable version of the ideas is probably https://www.kalzumeus.com/2012/01/23/salary-negotiation/, but for contracts
Nolo books can give you some basics on the contracting stuff. I wrote my own contracts, haven't had to test them in court but I guess they work.
At least one book on negotiating, I've used https://gettingmore.com/the-book/ but haven't done a wide survey.

> Do I focus on work closely related to my specialty or take a broad spectrum approach? I have no strong personal preference here.
My experience has been that I'm hired because an organization has a time sensitive need, and I'm plausibly qualified but (more important) highly trusted to flex into whatever they need. As an example, I mostly do ML in Python, but have been hired to do ML in R and Data Engineering in Python. But then, after you prove yourself, you get tapped to do all sorts of other things and you're pretty much a generalist.

> Should I prefer depth (fewer, more hours) assignments or breadth (multiple, fewer hours, perhaps get a wider perspective)?
I suspect you won't have much of a choice. My client's needs have always taken all of my time. If their budget were limited, I guess I would have tried to go parallel. But my preferences had nothing to do with it.

> What are some ways I can look for clients I can provide the greatest value to, other than engaging my network, especially for the specialist work?
That I don't know, I've only ever had two and they both reached out to me. I've had about 2 others make serious outreach in that time, roughly all people I'd worked with when I was full time.

> How do I price the work? Do I charge by time/sub-project tasks/whole projects? How would I determine the rates to charge?
The most important thing is to not beat yourself up for getting the pricing 'wrong'. There's no optimal answer that you will find if you just do a bit more research. It's almost always higher than feels normal, but you have to factor in the time you won't be working between gigs, etc. I also guarantee that some clients' expectations will be heavily non-overlapping: What is too high for some is almost laughably low for others. Obviously, it correlates to how much budget they have, but also just their random life experience. And how you frame it - your "hourly" will feel nuts but you're paid for solutions not hours. And you will probably leave when you pass the peak of your ability to provide solutions, unlike an employee who has to be supported while an optimal new role is found for them.

> If I have about two months until I can start working on this business, what are the most impactful preparations I can make?
Talk to old contacs (see my other comment). Do your personal finances to figure out your floor, but don't let that tie you down. Read the negotiation book and do whatever you can to internalize it - your first rate negotiation might happen faster in the process than you expect, and you're locking in many thousands of dollars in expected earnings.

Good luck!