One of the reason AJ is doing that because of his own principal that that he cannot ruin a woman's image: that's one of the main factor Antra is using against AJ.
Also his guilt + Bhootnis emotional blackmail drama along with her drama of attempt to suicide will make AJ marry her.
But I hope he has a plan or is doing drama
Technical it Antra & AJ cannot marry because Akshan are legally married they need to get divorced first.
Oh, I forgot that. But if Antra is alive and now she is returns, how years she needs to be gone, for Antra and AJ marriage to be considered invalid?