I’m not sure how much this helps, but I’ve had it bookmarked and I’m sure it’s worth a read: http://ultimatesatverbal.blogspot.com/p/how-to-study-for-sat-critical-reading.html
Maybe you can try switching up your passage reading technique? I found that breaking it up into small chunks and taking it question by question really helped.
Anyways, if you make sure you don’t miss any vocab, 3 wrong should get you a 780+, which is already great.
Sorry I couldn’t be more helpful 
, passage reading is pretty tough to improve. Good luck!