630 - verbal strategy

I gave my exam yesterday and scored a 630 (Q47, V30). My overall GPrep scores were a bit higher than my actual score (around 49 in Q and 35 in V), although I think it's ironic since I scored a 620 on my first diagnostic GPrep back in may/june. I have been studying for the past few months, but my verbal score simply has not been improving.

I am hoping some of the experts could help me analyse + improve my verbal score.

For SC, which is my weakest area, I have read the mgmat guide twice and made notes as well. I can now pretty much explain the contents of the mgmat guide, which apparently is of no help since I can't do SC questions/perform well. I am told that SC is most logical area/where you can do really well in the verbal section. However, I seem to know the rules but can't perform?!
Also, I have done the OG+OG verbal at least twice and do understand the errors (or at least would like to believe that I do!) and remember the answers somewhat.
What am I doing wrong/should I consider another approach for SC? or do I simply need more practice??
I have not done the 1000 SC Qs as I understand that some answers are wrong.. would a lot of the users recommend that resource even though the answers/source of Qs is dubious?

For CR, again, I've done both OGs at least twice. I intend to read the powerscore CR bible this time around. hopefully that should do the trick?

For RC, I have identified a good method of reading the passage that works for me, but still need to practice.. (done with OGs too)

Most importantly, could you pls recommend good sources of practice (besides OGs) for each section? I already have the mgmat Qbanks.

Thanks!!