I am a something male. I don't think people really understand how lonely it can get, unless you are married to one. And that my friend, is just a hint of the extent of the brain wash that Mormons experience. Dress nicely, as the girl will appreciate the effort put into looking good for her, and encourage her to do the same. I completely relate to all you've written; many of us have come to see Mormonism for what it is, and the severe damage it does to human brains. And even longer when you add that one-year fellowship to the end of it. Even without temple covenants marriage is a noble and worthy institution. The odds are definitely not in OPs favor for something like this working for him.
I think the LDS have been vastly over-simplifying that doctrine. Should either of you sisters raise your children and wonder what faith will they choose. Do not expect anything long term. I am a happily married mono-faith guy who has no testimony of dusted base boards. We have been married a mere 3. I guess I was just hoping there was way for it to work. I have been dating a surgeon and we are thinking about marriage. I am a very independent person socially so I often do not think to call people just because I am fine doing things myself.
Marriage offers a chance to develop generosity of spirit and a willingness to be improved by the one we love, no matter what faith tradition he or she may claim. Let's talk about kids. It's not fair to put words in her mouth and thoughts in her brain like this. She will never retire.
I don't think you should abandon the relationship just because she is lds. It's easy to be blind to deal-breaking faults when you are young and in love. She might not be keeping the Word of Wisdom, living according to the Law of Chastity, or attending church regularly. Since her father is a bishop, I'm sure he'll want to have his daughter marry a temple worthy person.