Well, it seems perhaps you know everything except what you need to know: where is his heart really?

If you can't find out directly, I suppose a clue could be, does he seem to love to hug you when he can; another possible clue is, does he seem to want to kiss you or look deep into your eyes?

Most basically-straight, maybe somewhat-bi guys who just do mutual j/o for relief or to make their friend happy are not into these gestures of affection. Mind you, some gay boys are too hung up to kiss at first, but for most it's pretty irresistible. Some gay boys, in fact, are very mechanical about sex and don't do gestures of affection at all, but my prejudice would be to write them off as potential partners anyways unless you are similarly inclined.

I think your interest in finding out, besides the matter of 'will he love you,' would be 'where do our activities stand in relation to his troth to his girlfriend?" (if you don't mind me using a nifty medieval word there that seems appropriate when I don't know quite what sort of relationship they have).