[Eric shrugged a bit. It's a 'you're welcome' of sorts. As to how he would have fought if Stefan had attacked him, Eric isn't making any assumptions beyond the fact that his will to survive is immense. He believes it gives him a certain advantage, but then Stefan might carry the same will as far as he knows. Eric operates under the assumption that he's the biggest dog in the yard, but he's smart enough to know that making assumptions about another's ability will end up getting him killed.]
There isn't even a scar. Thank you for asking. [He won't mention that his blood has startlingly fast healing properties, although Stefan might figure that out for himself as he did see Eric give Sookie blood and it's far too soon for Sookie's hand to be entirely healed.]
Elena is quite protective of you. [He's sort of inquiring as to the nature of their relationship without outright asking.]