Hi @ryanb,
Question 1)
I would have to see some code to answer. There are multiple steps to creating a block.
Question 2)
They really accomplish different things. Customizer is mostly about tweeking the design of items on the page while ACF is about adding content to the page.
Question 3)
This is a tough one. Basically, you are on the right track, but making block template pages is complicated. Here is a link to the codex: Templates | Block Editor Handbook | WordPress Developer Resources
This might work. I haven’t done enough with Gutenberg to really give a great opinion. Hopefully other users can comment. My thought is that you should try to do this on a small scale first to see if it works. Sorry I can’t be more helpful.
Cheers,
Bob