She started crying when I explained this to her.
But it is important to be ruthlessly honest with yourself about how you feel about it.
The religion rather, and more importantly, the church itself is integral to most mormons' identity. This man basically tells you in a simple way within 6 minutes.
The fact that she's planning to go on a mission should help. The most important thing is an open dialogue, as you say, and utmost respect for the other person.
At the very least, I might have tried to persuade my husband to pursue a different career, if only a less-demanding area of medicine. The extent of other physical activity depends on what you both want from the relationship, though in general the Mormon Church frowns on sexual contact even beyond intercourse.