NoWoRRyMaN
Here's my theory as to how he's able to put up a fight against her. It's not because he's the protagonist and the protagonist is supposed to win or anything stupid like that. It's because the system is acting as both a method of strengthening the players while also limiting their true strength, the same as in The World After The Fall. Because if he isn't dying after taking damage when his HP was previously only 1, that would mean that his actual HP (and possibly his other stats too) are actually a lot higher than the game says they are. So now that he's in a place where the system is weaker, the restraints on his stats are loosened, which results in him being much stronger. If my theory is correct, then everything would make logical sense.