Personally, I agree with you that he should not be masterbating with the baby
in the room and would be horrifiied he did this
in front of the
child ,but legally, I don't think you have a leg to stand on.
You say you are trying to get custody of the little girl, is this your daughter or the grandparents? Regardless, I would fight for the supervised visitation. But, this is just my opinion. What does your lawyer say?