I saw the case you quoted and think the woman likes your hubby. You should tell your hubby you don't allow them contact because their relationship seems abnormal. Why a woman will call a wife's bubby so night and know where he go? However, your hubby has problem too. If you still love each other, try to do that.
Dear Yoman,
Hope you and your hubby can solve this problem. Actually, I think your hubby knows you are not happy about this. However, it is not too worse until right now. Don't say 離婚 too easy. The kids need their daddy.