Capri,
It seems your mother has very little experience in treating you, or your FH, like you both are adults. Your FH is right in saying he does not need another mother.
You should have a talk with your mother and let her know how inappropriate her actions are. She may run ramrod over things in her own home ,but she cannot and should not be allowed to do so in anyone else's. She was being disrespectful to you both, and she has to be made to realize this.
After you are open and honest with her, you need to not go back on what you know is right. Don't continue to condone her actions - by doing so, you're facilitating her continuing to act in the same manner.
Stick with your FH and stand your ground. Once your FH realizes you're on his side, he'll be more relaxed.
So your mom has issues?! I'm sure his mother would have some of her own issues, if she were still alive. It's all part of meshing two families - there are tons of adjustments that have to be made by everyone.
Good luck!
Many waters cannot quench love, neither can the floods drown it. - Song of Solomon 8:7