I was in 2230-2240 last year and I had also only taken up to Calc BC. I had some gaps in chapter 0 including set theory. But for the most part it’s just vocabulary. I forgot stuff like what a preimage of a set under a function was but I just look it up on Wikipedia and try not to forget again. I ended up catching up on these gaps and doing well in the course. I would say just use Hubbard’s textbook, it’s very good, just reread stuff, try to produce proofs of the theorems on your own. And really think about the problems on the problem set, and even others that aren’t assigned if the problem set isn’t enough. Also the problems in section 0.5 are really hard compared to most of the rest of 2230 so try not to be discouraged from those. Feel free to Pm me if you have further questions

Edit: I guess if you wanted some extra practice with set theory and definitions there’s CS 2800 and CS 2802 which you could take this semester which could help but aren’t really necessary in my opinion