LOP is determined by the arm length. There are some videos in the internet detailing ways to measure your ideal lop HOWEVER, they will differ between shooting off a bench or prone, so you'll have to decide that first. Your scope will probably set farther forward if shooting prone as compared to off a bench.

For action screw torque, http://www.accurateshooter.com/techn...torque-tuning/

You can get the longer screws at any home improvement store.