This is no fairy tale, child. He is no charming prince cursed into monstrous form; the man is twisted all the way through and no true love’s kiss will ever change that. If he saved you from monsters worse than he, it is only because he knew it is what the one he loves would have done and would want him to do. Duty to the dead, not pity for the living, moved his hand. You yourself did not particularly factor into the decision and he certainly spared no thought for what might befall you after his timely intervention. One more young soul for the streets to swallow up, just like his. So it goes.
What do you think will happen when you follow him back to the home you imagine as a castle but is in truth merely a tomb? Do you think that if you scrub the dried bloodstains from the once white carpets, if you dust and mop and prove yourself useful, he will let you stay? That he will become like a father to you and raise you up from pauper to princess? There is no love left in him, not now. No kindness. At best you can hope to huddle in his periphery, protected from lesser predators by his presence yet too inconsequential to draw either his effort or his ire. But make no mistake, child, there is no happily ever after for you here. Not for anyone.