Well I think the reason I is more applicable for now. He never believed in the institution of marriage and the probable reason is because his parents had a bad marriage. He has feelings for Khushi but I don't think he wants Khushi to reciprocate because of the reason no 1. He really doesn't want to fall in love, he just wants to bury his feeling just some where deep down inside. But with the every coming day his feelings keep on getting more intense at every sight of Khushi. That is what infuriates his anger at her every sight, as he is a total control freak but when it comes to Khushi he becomes helpless.
But I have a different take on this issue.
1.Arnav never really wanted to live in a live-in relationship with LA. He had brought her to the RM only to challenge Nani.
2.Arnav now desperately doesn't wants to marry to challenge Khushi
5