I'm already too late to this but I'd skim the maths stuff to just get your brain to start processing it and acclimating to doing it but with a clear commitment to not expect anything from myself, just to give it a quick looking over.

You'll probably understand more than you realise at the time you're reading it, you'll likely be thinking about it between that point and the next time you pick up the work, and hopefully it won't feel as overwhelming because you have started to confront it and it's not as bad as you first thought (this is less effective for people who are a bit prone to catastrophising so ymmv).

I was in a similar situation a long time ago and ended up having a breakdown. My main advice is to focus on whatever is absolutely necessary and don't go in without an exit strategy; you surely don't absolutely need to do all of it, weigh the benefits against how stressful it is.

I wish I had a tip for how to actually go through with doing it and doing it more effectively, but that mostly lies on being in the right headspace to learn new concepts which is hard to do when under pressure.

Edit: oh yeah and also sleep well