Modern Classical Physics is a great book - I've recently started working through it (just about to move on to chapter 2). I'd be interested in chatting about it with others/cross-checking solutions. Anyone who's interested, drop me an email (address in my profile).

If you're thinking of getting it but want to check it out, there's a 2012 draft version that the authors have previously taught from here: http://www.pmaweb.caltech.edu/Courses/ph136/yr2012/. It's not the same as the book, of course, but from a skim it seems quite similar.

Does Slack let you write LaTeX?

I would love to join a reading group (on slack or another messaging platform) on this book.

Depends on what the math re-learning covers. You'd need differential equations and 2nd year calculus.

A good choice for less math might be "Gravity from the ground up" by Schutz.