To be very honest, it's not just just mother that is the issue here. If she is toxic, that is her issue. If you allow her to treat you, your children, and your fiance this way, then it is YOUR issue.
It sounds like you could be an enabler. Enablers tend to allow toxic people to treat them badly, manipulate them or put them in impossible situations. They will either just go along with it or make excuses for the toxic person, because it's easier than standing up to that person and making that person uncomfortable. That might not describe your relationship exactly, but there are some real similarities. You mentioned that you've done a lot of growing up and maturing, but I have to tell you that allowing her to treat you this way is NOT a sign of maturity. Maturity is having healthy relationships around you. It's great that things are changing in your life and you aren't reacting to her anymore like you used to, but you may have a false sense of progress if you're still willing to put yourself and your kids in such an unhealthy atmosphere.
I hope you take to heart what the other posters said about trying to find other ways to honor your religious beliefs until the wedding, but without living with your mom.
Living with her may help you stick to your spiritual beliefs, but it makes your spirit sick.