My prediction is this. I don't think this is the end of the Atharva track. Cause Anu kept saying that if bhoot drama is discovered, it will be hard for KalMa to get custody.
Basically, now, Athu has no grounds to file for custody since Sampu is dead and KalMa cannot sent Athu to jail without admitting to bhoot drama. So custody will remain with KalMa for now, and Athu will find another way to get custody. So Sampu death is a reset of sorts.
I am sure AnuSar will advise KalMa that before Athu finds another way to file for custody, you should have another child (since that is their favorite dialog). They will probably try to prove Avni is faking the mental illness to get her to blame Athu for Hari's murder, but she will probably get caught for it instead.
Finally, I feel Athu will get caught in a drug smuggling case. That will be why he came back to AN, and needs Nal Emporium and Moksh.
Yes, this seems the most logical explanation to retain Atharv.
As you said Atharv didn't come out of the love for Moksh. His intentions are yet to come out in the open.
Moksh is a means to divert KalMa or rather Malhar from his actual intention.
And agree with you Avni's exit would be most likely for the Hari murder case.
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