In a lot of ways, getting into medical school is the hardest part. Once you’re in, they make it really, really hard for you to leave!

If you’re willing and able to move around the country, you
can get into a school if you’re a decent student (and it sounds like your fiance is). WRT the MCATs, you honestly don’t need more than the required prereqs in order to do well. If he’s really worried about the test itself, he can always take a test prep course.
In my experience, med schools are eager for those who stand out from the crowd- and having an English major could be a real benefit that way. Sounds like he’s got his head on straight and knows what to do in order to make his goal happen.
As so many have said, I don’t think it’s really the doctor/surgeon thing so much that needs to be discussed. You need to figure out (and maybe you already have) if your priorities about life, work, and family balance mesh with your future husband’s. If he’s a workaholic, it won’t matter if he’s in medicine or law or business or computers. He’ll still work 70-hour weeks and travel and be away from home too much for your well-being. If he’s committed to family and to *being with *his family, not just financially providing for them, he will be able to make that happen as a physician. You may have to put up with some rough years in residency, as he won’t have much control over his hours during those years, but he will be able to spend time with family, if that is his priority, once he is finished.
Also, residencies vary widely- a general surgery residency is only 5 years, and primary care residencies (peds, internal medicine, family practice) are only 3, but fellowships (cardiac, pediatric, transplant, etc etc) can easily add another 5 years to the mix. Depending on what he does, he doesn’t necessarily have to be in training until his late 30’s.