And I think the most frustrating thing my brat does now is anytime my husband and I are trying to have a discussion it's "mommy, mommy..." And I try to tell him to stop but nothing seems to be working ..
Hard to do - but try ignoring him. You've probably already explained that he should not interrupt when people are talking. 2yo's have no patience. (like you don't know this!) However, since he already knows it is not polite to interrupt - do NOT reply - no matter what! Get up and walk away if you have to. Then, when he is NOT interrupting you, praise him for being so polite.
Hopefully, this will help break the cycle.