pump under sink help

I'm going to install a pump under the sink in my garage so that I don't have to drag all my equipment up stairs to clean it. I want to install the drain line following the red line in the pictures below. I know I need about 1/8 drop per foot and a foot valve, but about how high does the foot valve need to be and do I need a vent line on the pump box or on the line at the high point? Also, should I install a garbage disposal in line before the pump box so grains don't clog the pump. I don't know if it matters or not, but the run will go up about 7ft then go 9ft into a 90 and go another 28ft into existing plumbing that is in the hole seen in the picture.

Then on the water side I want to tap in before and after the water heater, is that ok to do, or do I need to find another source for the water?

You'll want the check valve as close to the box as possible, so the water above it will force it closed. You'll also want to vent the box.