do you think, when he does get intrigued by someone romantically, that the desire can become consuming? it appears that in general Alucard feels things on a much more deeper and maybe even visceral level
Honestly, I think it might. Supernatual beings are frequently described as having heightened senses. Heightened emotions are a part of this. When you really want someone in love or lust there can be an intensity that has a way of altering your entire perception of reality. Alucard is an emotional being and quiet. Quiet people digest the world in such an internal manner so it makes sense that an emotion of that kind can become consuming. The real question is how consuming can it be?
When he desires somebody, he wants to be completely submerged in them and everything they are. Sharing each part of himself and having them do the same. But the desire of that level of intimacy doesn't mean he'd be able to do it easily. Wanting to be loved doesn't lessen the trauma of the past and that trauma can create quite the obstacle in an all consuming submissive and dominant position in love.