wow! I know this isn't what you want to do, but i would change all phone numbers and try and cease contact completely. You can't have that type of stress when your pregnant or when you have a newborn - its just not right.
I wouldn't want my children, or my husband to be exposed to such things... so in my mind, you've tried.. thats all you could have done.

As for them ringing our other relatives, maybe you could suggest they also change their numbers? OR if they don't think thats necessary, then simply ask them not to call and tell you about the abusive calls.

Sorry i know i'm not much help, good luck