Kirsten, I am sorry that your mother and her bf are such ignorant jerks. I understand that you don't want to fight with them, but it is not healthy for you, your back, or the girls when you feel angry and disrespected. I would consider not inviting them back into my house if I were in your situation. The rule in my household is that I must respect you before you are even let across the threshold and if you harm or scare my little family that is the last time you are permitted across the threshold. Your home is a reflection of yourself and your safe place, do not let these people destroy that.

Next time maybe invite some friends over (besides friends are usually better than family any day )

Cheryl