Catholics basically married catholics and protestants basically married protestants. Go on dates on days other than Sunday. Is he aware that if your children are faithful members of the church they might end of marrying in the temple and he would not be allowed to attend the ceremony. Some exceptions and valid reasons do exist for divorce but self righteousness is not on of them.
Don't let her try to bring in the missionaries to explain; remind her that she is an RM and knows all they do and probably much more. There are billions of other girls out there who I wouldn't have issues like this with. JS married a girl her age when he was 37, after having told her that he had been threatened by an angel with a flaming sword and promising her entire family salvation if she consentedI decided to read the ces letter.
I guess the only risk is your husband having an affair with someone at work. But life is long and eternal and all righteous people will choose the right at the end. No I dont think so. If she won't reason with your investigation of the church, nope on out and go on your merry way. As time has gone by I realized that the opinons of others is not important to me and oddly enough those who did not originally approve have had their hearts and minds changed by the love my husband shows me, our daughter, and the members of my family. I have found strength I never knew I had but if I knew then what I know now, I might have made a different decision. That was literally over years ago. But it is important to be ruthlessly honest with yourself about how you feel about it. Things are very hard for me right now too.
Stop trying to make up for all the little things you miss with big short-term things. I think that if these two really care about each other that she should be told to take a moment and ask herself how she would feel if they break up over this and years later she finally researches her religion. This makes them overwhelmingly successful wives and mothers. The important thing is that you are getting to know one another, not that you are always doing fancy things. This insecurity is at the root of the princess syndrome. The Mormon church is certainly a time consuming church.