She is both possessive and insecure of him and his love and that fuels her actions even more. Now along with controlling Arjun she wants to control everything that touches his life- from food, clothing to the people he loves.
Arjun has no choice but to accept since consequences are almost always dire. It's unclear if he believes her rape allegations or not, because almost immediately he goes back to suspecting her and not wanting any of his family near her. Arjun is trapped and essentially ill equipped to deal with her because .. cmon who is? Nobody marries a hot successful, seemingly living woman to realize she is bat shit crazy. I believe in the 3 years, he was estranged from his family, Saanjh, so there is lack of motivation to even try. I believe Jhanvi and Saanjh are key in him smarting up and divorcing her.
To the discussion should Arjun have discussed his problems with Ayan: in the most straightforward sense, NO. But, the brothers were once close, thick as thieves and separated/ estranged by Maya herself. For 3 years, Arjun had had no friends, family, and that was his ONE night of freedom. So he is very well justified to vent his frustrations, emotions to his brother/family. He is human, and we as audience can see what he can't.., His brother was foolhardy to not heed Arjun's words and just barged in and got trapped. Sometimes good people with great intentions do stupid shit and get caught regardless.