I think it has more to do, with the way he perceives of Aaliya. He knows that Aaliya is one simple, innocent, deeply cultured & valued girl. She doesn't fit into the criterion of girls he dates or he has dated. That's, I believe partly the reason why he wants to get rid off her or push her out of his life, before he becomes attached to someone like her.
Plus, Zain I'm sure also realises, what intimacy means for a girl like her. If this hadn't been Aaliya and he'd have had to forcefully, marry someone of his kind, he'd have definitely taken the step, even if that meant, they'll file for a divorce in less than a month's time. Since this is Aaliya & she is different, so despite all the trouble he causes her, I guess he also feels a certain sense of responsilibility towards her, keeping in mind the whole family scenario, the accountability that comes with it and also the fact, that he wants get rid of her & get back to his old ways.
So, probably, as of now, he doesn't see a point in getting intimate with her :)