Lets!
Dramatically, John is very good at dodging bullets -- that's his super power combined with his quick thinking and stamina.
We can think that all of those gun battles wear him down, and obviously he has the wound on his foot (but even that didn't seem to slow him down that much either).
In the final scene, he's clearly fatigued but still quick thinking, and quick reacting (and apparently his hands were simply filthy, not slick with blood). So whatever damage he did take during the entire encounter did not seem to affect his overall ability.
To be fair his true, actual weakness at this point of the story is simply he is out of ammunition, thus the ruse and interplay at the end.
Even Holly, while a potential weakness as hostage, likely wouldn't have been had John has a full magazine and decided to get the drop on Hans and Thug #7 before Hans could use her as a shield.
Not a very dramatic ending, but there you are.
No. I've never heard of this.
Not sure what the massive damage rule it, but if it's "Level 10 characters have 100 HP, but a magnum with an extra success does Enough Damage(tm) no matter what" seems to kind of make the HP moot in the end.
