I have a stepmom also and if you don't feel comfy calling her mom, then don't. I call my stepmom mom, but not in front of my mom mom. If that makes sense. But I love my stpmom dearly and she has been in my life since I was about 5/6. Early on before her and my dad even got married I called her mom (I was about 8/9) and accidentally did it in front of my mom when we were in a parking lot (met my mom there so I could go with her) and she was furious. I didn't call stpmom mom again after that for a very LONG time, but I do now. She is just as important to me as my mom. Sorry for the ramble, but I think it is important that YOU feel comfy with what you are calling her and if mom isn't comfy, don't say it. I know not everyone is fortunate to have a stepmom like I do and I am grateful that I got the one I did. :O)
As far as the sticking the noses where they don't belong. My personal advice would be to talk to your dad and TRY to politely tell him that he (and her) need to butt-out. I don't know how old you are, but I am guessing that since you have a 7 yr old, that you are over 18. So I would tell you dad that you are an adult and you will do things how you feel they should be done and if they don't always agree with that, they should keep their opinions to themselves. I (once) had to actually kick my mom (not stp mom) out of my house because she was being disrespectful to me and was critizing my house and how I was raising my son, so I told her she needed to leave and if she was going to continue to do so, that she shouldn't come visit our home again. (That was 8 yrs ago and she still critizes and I have since moved, but she only came back to that house once after that) and she doesn't come to my house very often - parties/family get togethers is all and other people are around, so she doesn't say anything rude at those times).
Again sorry for the rambling, but unless you live in their home, I would tell them you run your house as YOU see fit and what you do under your own roof is YOUR business and YOUR choice. They can't control what you do in your own home and if they don't like it they don't have to visit. Kind of like the saying "if you can't say anything nice, don't say anything at all" I would also explain to your dad, while you like stp mom, you aren't comfy calling her mom and that you won't.
I know I am in kind of the opposite position as you are, but please feel free to send me a message if you need/want to vent or just talk to someone about it all. I feel for you!
I wish you the best of luck!
Prayers and hugs! K.