Hey!
We are in the same boat, it seems! (I want to apply to all the same schools you do as well). I've been able to raise my PSAT score from soph year from a 163, to a 195, (and get my SAT to 1990; I'm taking it again in January and I'll hope to top that by 60 ish points)
I had a lot of struggle with CR as well. The first step is to gain a good vocabulary, which can be done in a lot of ways. I learned by taking practice tests and looking up every word on Sentence completion which I didn’t know. I also got the app “visual vocab” which teaches you each word and gives you an image behind it. It helps your retention of words.
However, the best prep method for sentence/vocab is getting the book Direct Hits (Volume one and two) They have all the words you need for the SAT, They’re a great help!
http://www.amazon.com/Direct-Hits-Core-Vocabulary-SAT/dp/1936551136/ref=asap_bc?ie=UTF8
For passage based questions, get “The Critical Reader” by Erica Meltzer , it’s a book that hones in on CR topics.
Additionally, check out this guide
http://criticalreadingmethod.blogspot.com/2012/03/how-to-attack-sat-critical-reading.html
Hope this helps!