You gotta kick that mama's boy to the curb. A real man loves his mother, and treats her with respect, but keeps her at arms length. He is devoted to his woman, but does not need a mother anymore, because he is a real man. He chooses a lover and a partner, but does not need a mother to coddle him. That guy will turn out to be weak in a crisis, and will need her to play the mommy role eventually. How gross is that? Just my two cents.
It won't get any better than this.
If this is unacceptably awkward, you have to get out. At the beginning of a relationship, his mother and the boyfriend are on their best behavior and if this is the best she is getting from both of them, it won't get any better. Imagine having children and the grandmother role she'd play in the situation? No thanks, I don't need his mother trying to mother my children and having her push that in my face too!