I am not a native speaker either, and I do have a similar experience with highly technical words or the words that are narrowly/rarely used. Since you don't have much time left before the test, I don't think reading the Economist
or carrying a pocket dictionary will help you much.
The strategy I have and the one that worked for me in CRs and RCs is what I call "renaming". When I see a word I don't know, I just assign a name or a term that I know and say, ok this "turnip" is actually a "tulip" or whatever works in the context of the paragraph. The thing is that none of the CRs or RCs or SCs is going to test your knowledge of a specific term. It's the content and context that you are tested on. Trust me, a lot of native speakers are not familiar with technical terminology used in scientific RC passages either. The key is to not get caught up with unfamiliar words and just try to understand what the paragraph is trying to say in general.
This strategy will work most of the time but sometimes it won't. I have an anecdotal example that shows when it's not going to work. In my first GMAT attempt, I encountered an RC passage that talked about deities and some kind of figurines. I know that some of you will laugh at me for not knowing exactly what a "deity" means but at that point of time I had no clue. Anyway, I used my "renaming" strategy and decided that a "deity" means "clan". I read the passage very carefully, trying to comprehend every single word.
Guess what was the 1st question that I got? Well, it was something like this: "what is the best term to describe the author's tone in the context of describing the deities mentioned in the passage?" It got even worse because the choices looked something like that:
A) Vehement blah-blah (blah denotes the word I have no idea about)
B) Insightful doh-doh (see blah in 1 for the definition of doh-doh)
D) Critical yet doh-dohblahous
E) **?!@#ful - Huh?
I stared at the choices for a while trying to eliminate at least one. Decided that the tone couldn't be vehement since it's too strong of a word, so I picked Blahodohcious (C) and moved on.
Clearly, this is a great example of why broadening one's vocabulary is a great idea in a long run