I don't quite agree with some of your posts. So I'll pose my theory behind his healing powers? I'll start with a normal person. A normal person has these abilties to heal: blood clotting, cell repair/mending, cell replication to replace lost ones (blood for example), immune system to prevent infection, adrenaline secretions, forms of chemical numbing and excretion of harmful poisons, etc. Wolvie doesn't have any extra ones.
Right off the bat, a truck splattering a normal person prevents many of these abilities from working because of pure shock, which prevents the body's healing system from working correctly. Wolverine by contrast, can easily get over pure shock. He fell out of the sky in HoM and landed on a building. He retains consciousness almost immediately.
The above abilities listed, are accelerated to such an astonishing rate that while a normal person could heal up a scratch in their liver and not much more, Wolvie could heal a gutted liver just by virtue of speed. This applies to everything, muscle sinew, blood, blood vessels, organ tissue, skin, nerve tissue. Its probably so fast, that while he's being damaged, his healing system is probably at work, whereas ours would take time to even start. If you apply this to a scene where some villain telekinetically rips his entire heart out, the remaining blood vessels that were connected to the heart are growing back the tissue at the stubs. Those cells in turn are growing back the tissue that immediately antecedes them and so on and so forth until he literally grows a new heart. Since the body's entire design is found in the DNA in every cell, by virtue of speed, we can see Wolvie surviving this type of massive internal damage.
Now, scientifically, Hulk's punch is equivalent to the force of a bomb. That's an instantaneous one time injury that could rearrange and maybe liquefy Wolverine's physique. But his body's cells remember the original design and could probably rearrange it fast enough to survive. So why isn't he a red smear when he gets whacked everytime? I happen to think that the adamantium absorbs a ridiculous amount of the pressure and distributes it throughout his skeletal system, taking the brunt.