If you don't mind me asking, have you thought about taking a class maybe? Also, you need to make sure you really understand each and every type of question in Verbal, especially when it comes to SC, from the books you're studying from. This kind of constant exposure will give you familiarity and you'll be able to identify a key error within a minute if you're really tuning yourself to work that way. Also, as Spoilt mentioned, it's not about the number of times you do the questions in the practice book, but it's about the concepts you learnt from it.
I would suggest taking a few days off, and then restarting with your preparation. You haven't posted your section score split up, and it might be easier for other experienced members in the forum to give their input if you post this, so please do so.
Manhattan SC, OG 12, OG Quant and Verbal should be enough mostly. Use Powerscore CR if you can get your hands on that. Maintain an
error log. Time your answers. Review the weaknesses accordingly.
Hope this helps!