A photo is often very deceiving about leveling issues. Suggest you actually measure front and rear to see if it is off. If it is out of level, measure from the ground up at the front of the frame, and then from ground up between the wheels to the frame, and that will tell you how much correction is needed. Measuring front/rear will exaggerate the problem.
Conventional wisdom says 6" minimum between overhang and bed rails. And that's if you stay on good paved roads. I have 7" and would not want any less, but we get off on dirt quite a bit.
Don't worry so much about torque on the pinbox bolts. Just get them tight. It is not critical. But if you absolutely must use a torque wrench, just google torque values based on the bolt diameter. Go with the grade 5 values. That will be plenty even if you happen to have grade 8 bolts.
I disagree that towing low in front is better than high in front. If you're going to be out of level a bit, high in front is what you want. Nothing tows well when the front is low.
2006 F250 Diesel
2011 Keystone Cougar 278RKSWE Fiver