I somehow doubt that he considers Devi as his Maa because he still addresses her as badi maa, talks about being his only mother or Maa se badkar but he has not addressed her as Maa and somehow despite the wall of differences between Shaurya and Shaan he still seems emotionally close to his father.
His equation with Badi Maa seems to be that of Respect and Gratitude and nothing more. I mean he definitely loves her but as one would an aunt but that seems to be it. Even the affidavit that he made seems like an subconscious excuse to contact Aastha, challenge her sever ties with him legally but desperately wanting her to reject it.
I think this stems from the fact that one Aastha Sabarwal will always be his mom in his heart even if his head fights it, because when it comes to Aastha he is still the four year old boy that she left behind how can a four year old hate his mother? He can stay angry and cry for attention but not hate. Another factor could also be that he has consciously shut out Badi Maa because if "Maa" can abandon then why can't Badi Maa? In a way Devi's own poison has worked against her.
There seems to be line of boundary in his interactions with Devi because he never demands anything as one would of a mother.
What are your thoughts?