If you really feel that strongly that you want to be a nurse, do it. No matter what. I just finished going to school full time (15-19 hrs/semester) for 18 months, while working full time, and I have a husband who is also a nurse and two children as well. It CAN be done. (Oh yeah, we bought our first home and moved during this time too!)
It will not be easy. Once the children learn to adjust, and they will, and your husband realizes that that he will have to learn how to make hamburger helper and do the laundry, (ha ha) things will calm down a bit.
Take some of the pressure off of yourself by realizing that maintaining a 4.0 is not you primary focus at this point. It just isn't. I had to deal with the same thing. Instead, sit down by yourself in a quiet moment and prioritize EVERYTHING in your life. Assign everyone and everything a number, that means your spouse, children, laundry, dishes, lawn, school, relatives, friends, etc.... That is the only way I was able to maintain my sanity and not feel too guilty about saying no when others made demands of my time. If one day schoolwork is priority #1, and there is a family birthday party for your mother in law, you can simply look at your priority list and see what needs to be done. AND take time for what matters most, yourself and your family, at least a few un-interrupted hours every week. Make it a family "date" where you don't discuss school, bills, problems, etc..
As far as the A&P class, It WILL get better. Chances are, with your GPA, not many (if any) in you class did very well. She can't fail all of you! Review your concerns with your professor, and examine how he/she tests. Learn to focus on the things that he/she deems important instead of trying to learn everything at once. It just can't be done. If everyone did poorly, chances are the professor will revamp the class presentation, or focus more on testable content.
HANG IN THERE!
I hope this helps.