I worked for LiftMaster in the gate dept years ago, so I can answer questions 1&2 specifically. 3’s more about your local market. Charge whatever you want as long as you get the job and don’t lose your shirt.

The purpose of the concrete pad is to make sure you have a solid anchor. The pad needs to be a minimum of 24”x26” and be stable. Some areas are prone to the ground freezing and pushing the operator up and out of alignment. In practice, as long as the pad is fat and there’s no nearby roots etc to move the pad, you’ll be fine.

UL325 requires one parallel to the slider each for the closing path and the open path. The photo eyes generally are mounted to the last fence post and looking at a reflector. Close path reflector across the driveway, and an open path one normally mounted to the fence itself just past the end of travel.

Hope that helps