For a front firing, rear ported (H-100) subwoofer, how far away should it be placed from the wall?

2-3" is plenty. You just need a little clearance for proper air circulation in and out of the port.

what about how the sound bounces off the wall?

Around 3 inches would be fine,you may want to experiment with placement and try a bit farther from the rear wall.

The bass will bounce as you say it,when you have reflective surfaces they reinforce the output in the lower regions. Room gain in other words,the more you place it in room the less room gain you get.