What a perfect analysis. No matter what he says about his mother being his dil or dhadkan or whatever, Dev needs Sona like he needs to breathe. He is incredibly dismissive of her this season, she is the wind that gives him flight. It's jarringly evident how bothered he is when around, he gets restless and uneasy. In season 1 when she was angry at him, he couldn't function till he ensured she accepted that phone (and his apology), similarly this season when she is upset and leaves to her father's house, he simply has to go fetch her that same night. It wasn't for the kids, the kids had already been put to bed, he just has to bring her back- there's no reason, he just has to.
You put it so well when you said he isn't himself without her. When you follow from season 1, you see a hopeful man grow in love. This season, we just see a weak man with mommy issues beyond measure.
Absolutely. He cannot take it, when things are not normal with Sonakshi. In S1, he couldn't take it if she was mad at him, upset at him, unhappy with him. Whatever. He couldn't function, would get really restless, anxious, trying to fix whatever it is. That phone episode was quite telling. They weren't even friends at that time.. I always have believed, he was in love with her much before she fell for him. He just realized it later.
In this season, they have shown him to be dismissive of her, but as you pointed out, he couldn't take it that she was at her father's house and had to get her back right away. He lost his temper and threw a tantrum by sleeping in the garden, but he hasn't had a moment's peace or a wink of sleep. He is desperate to get back to her and it shows.
I agree with your last line that the S1 man falling so deeply and completely in love is different from this S3 man.