I'm not sure what, if anything, you could do in 2-3 days to dramatically improve your verbal score. As SXCCY mentioned, your best bet is probably to cram-study vocab banks & hope a good amount of them stick. Reviewing strategies might be worth pursuing as well (e.g. if I encounter a TC or SE question with 1+ unknown words, how do I proceed?).

I mean who actually uses those GRE vocab anyway. If you use GRE vocab in grad school, then you are ignoring the most important rules in academic writing: clarity.

No offense, but this is not a good mentality to have and I'm sure that's (in part) why you've struggled with the verbal section. They aren't "GRE vocab words" that ETS is requiring you to memorize for no reason; they're words that educated adults use in formal & common parlance. You'll encounter many of them in your post-grad education, in reading for leisure, and in reading to inform yourself about the world. Granted, some of the more advanced words you'll come across in studying are a bit esoteric, have ten exact synonyms, etc., but the vast majority (as in 95% or more) of the words you'll see in word banks such as Magoosh's, Manhattan's, Barron's, etc. are words that you'll re-encounter in the future; forgetting about them because they're "GRE words" would be doing a disservice to yourself. They're used for that exact reason: to improve clarity, not to obfuscate. Good writing is as succinct & pithy as possible, and having more words at your disposal aids with that tremendously.