Why in a world where people are magically given unbreakable weapons would a blacksmith's primary job be making weapons?
Also he should be a craftsman instead of blacksmith, it doesnt really make sense for a blacksmith to be able to make anything
As long as people are told about the blood boiling technique and it's downsides before using it, I wouldn't see it as evil.
It's not like it makes people go crazy/murderous
He could still be a very good adventurer... obviously he wont be the best but he could enjoy a party that just wants to make a fortune and not try to be the best