Hmm, I like your question. You haven't asked general: "...I'm very bad at verbal, what should I do?" but pinpointed some issues you have trouble with.
As you can see, the majority of candidates have problems with SC. Everyone will say that you must have Manhattans' SC book and I will say the same - this book is a "must have" for every serious GMAT student. But, for me, it wasn't enough. In addition, I used various scripts made by people from this forum and elwhere.
Especialy, I've found some scripts made by Prachi - some girl from Malasyia. Her SC scripts are very detailed and comprehensive, I think you could easily find them by entering "Prachi idiom list" or something like that in Google. It is not just an idiom list but a whole blog - it was a real gold mine.
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