The nanites break down the bullets, and bone shrapnel as they regenerate the bones, and flesh. Also he's got bio-armor which come on he's from a technologically advanced planet, Its in the picture before you ask where it came from. So he's going to be able to lift a bit more then 200 pounds, 400 pounds at maximum if he's pushing himself. Along with take lower caliber rounds without any difficulty because I mean come on its armor. Though buckshot will make him go flying through the air, and leave him with internal bleeding. And finally the healing factor comes from the nanites, coupled with a minute regenerative ability. The most on his own he could heal without the nanites help would be a small deep cut, so a stab wound that didn't to in all the way.

I hope this has answered all of your questions.