A child has unconditional love for their parents. How I know that? Firstly, I just became a mom a few months ago and secondly I have unconditional love for my parents.
Now, Ishwari's behaviour is completely wrong. She has ruined the life of her son and daughter in law and is now trying to affect her grand daughter. ishwari is a flawed character where she is super possessive and selfish. He pride and ego is what is coming in the way of all relationships.
Having said that, dev should not leave Ishwari niwas or Ishwari. He would never be happy. Actually, Sona would not like that either, separating child and mom.
Instead, you need Dev in that house getting Iswari to confront her demons. You need Dev to get her to accept he faults. Apologize to him and Sona. Actually even if she doesn't apologize to him (unconditional love clause), she needs to apologize to Sona and the Bose parivar.
Dev needs to step it up a notch. Dev needs to live in the house with his mom and make her feel empathy.
Then Ishwari needs to reunite the family.
That's the track I would like to see.