LET YOUR HUSBAND DEAL WITH IT
Ultimately, this is your husband’s responsibility. I’m not saying dust your hands off and act as if it’s none of your concern. It is—this is your life together. But at the end of the day, your husband has to grow a backbone and deal with the woman he chose to have a child with. He has to be the one to set and maintain the boundaries, and keep his new wife and his child or children out of the crossfire.