This may sound a little harsh, but its' YOUR relationship with him, not his family that counts. So sit him down(hes' not a little child I am presuming) and tell him that for your relationship to work, there needs to be SPACE between all of you. Enough for YOU to feel comfortable, not him.
Because this is how it will go down-you will lose every argument. Everytime something goes down and baby does'nt get his way, mommy will be there to pick up the pieces. She will tell you that nothing you do is good enough for her baby boy. And forget about having children, because your mothering skills will be criticized to no end. And the phone conversations-they will be talking about YOU most of the time, so if this is what you want don't say nobody told you.
You have the right to have space between you and them, and if he does'nt like it tell him to get it over with and just marry his mother instead.
Just because this is supposedly typical behavior for dominicans does'nt mean it has to continue or be tolerated.
Don't sugarcoat it or run around it. If he becomes defensive and takes it as an attack on his family then you really have to ask yourself if this person is really concerned with your happiness. So remember a few years down the road when the invetible breakup occurs that Berzin told you so. And WHEN you break up, it will be YOUR fault.
5 cents please!!!!

Off-topic, but VERRRRRRRRRY important-I'm Gold, baby!! GOLD!!!! I forgot to celebrate my 500th post!!!!!! Man, that's alot of advice dished out...I'm worn out...think I'll go rest...in Sosua...yeah, that's the ticket....with a Presidente in one hand...and a WHORE in the other!!!!