[MamaS]

Well, you and I had the same situation, but handled it totally differently. I don't have any advice, but I do have empathy -- familial adoption is the hardest thing to do.
When I adopted my grandson, nothing changed for him, except the name listed as "mother" on his birth certificate -- and he hasn't seen that yet. He still calls his bmom and bdad "mom and dad" and calls me his "Mimi". He lives with me and mom and dad drop by for regular visits. They understand that they are allowed to visit as long as they respect my authority and my decisions. They know that they have no legal rights. So far (two years) this arrangement has worked out.
Your problem seems to be that bmom and bgrandmom do NOT understand, do NOT respect, and do NOT believe you when you say that you will end contact. You may have to actually DO IT -- then when they see that their actions have results that they do not like, you can renegotiate visits and relationships. I wish you luck.