Good question.
First, you didn't ask about this but I'm going to answer anyway. I haven't heard of many people going from 660 to 750 in one month. This is extremely unusual. You may need to think about whether you need to prioritize the time frame (in which case, your goal score may need to drop) or whether you need to prioritize the score (in which case, you may need to give yourself more time).
Next, on SC: remember than 1m15s to 1m20s is the average - you'll have some that are faster and some that are slower. The upper limit for SC is about 2 minutes - beyond that, we're usually just completely lost and we should have guessed and moved on a long time ago. :)
The questions you describe are really challenging, yes. Take a look at this first (just to make sure that you're working efficiently in general):
https://www.manhattangmat.com/blog/inde ... em-part-1/and then this:
http://www.manhattangmat.com/blog/index ... orrection/That second article has links to a bunch of others - follow them and start learning how to handle the sentences that have much harder splits!