Taking the advice that I've heard from the LSATdemon podcast: you should plan on waiting another year. I think that if you push it back a year and give yourself time to really study, you can get your best score. If you are scoring in the 140s in a practice test, you will likely score in the 140s during the real test, which likely translates to not getting accepted or getting a bad offer. I would wait until your practice tests are at your goal score i.e. 150s 160s 170s etc. and then sign up for the test.

I use both. If I get a question right, I will use the written explanations only if I want more clarification. If I get a question wrong, however, I will read all the written explanations, and then watch the video too, to ensure that I fully understand why I got the question wrong and how to get it right in the future.

I'll just echo what lots of people here are saying, and what I've heard various LSAT test prep professionals say, don't rush it, you can, and really should, take a year, especially if you are not scoring the best you can possibly do. Just keep studying until you get your best possible score, then sign up for the test. No need to rush it.

I think the point is to ignore the difficult vocabulary and just understand the argument behind the use of such complicated terms. I am guessing the lexical specificity is such in most cases that, unless one was actively involved in that particular field, few normal people would be able to understand it.