Uh.. he just described a psychopath to a t in this and previous chapter. Not sociopath, psychopath.
He even described the feeling people can at times get when working with a psychopath, it is this unnerving feeling that something is off (ofc, high functioning, high intelligent psychopaths can usually act in a manner that will make those momentary feelings a lot less prevalent).
Sure, he might, hopefully, just be a sociopath. One can hope, for both their well beings.
Still, a psychopath *can* experience love to some level, but not in the same way you and I understand it.
Either way, there is No "fix" for psychopathy. She is only going to possibly influence his actions because she is moving his opinions around. But the moment she dies, he will go back to the old ways.
And I agree with the rest. I don't like trying to tie the protagonist to this kind of person.
I am fine with a flawed person. But please don't try to create a story about fixing something that isn't actually broken, but designed differently.