It sounds like you have nailed the problem already; too much attention for the wrong behavior: you are feeding the sep. anxiety. You are rewarding demanding and rude behavior. With "rude" I mean behavior that a more dominant would never accept from him.
My advice: put your boy friend first. If the dog takes his place or sits on you, put him in a time out (the dog!!). Give him more to do.
Deja, GSD, sable WL, female, born 11 / 2013
Cam, Rough Collie, sable, male, born 8/2015