I have a theory about kabir.
1. He is done with the revenge so he is trying to unite the families. Both will not agree to it , so he has taken this route to make Pooja and Mittals agree.
Other than that I don't find any valid reason for him to do this wedding.
He is playing a Salman Khan from the film ready.
That's why he is taking care of her mother. Someone already mentioned in the forum that he is a fixer.
The way he is staring at Pooja makes me think that he is in love with her.