My DH and I met in grad school and dealt with a long separation while I was in China doing fieldwork (even though he is the one originally from here, ironic!), and we're now 16 years married with two Ph.Ds, 2 kids and 2 jobs in the same city (kind of -- DH has to be in another city one week a month for his), so it can be done! How essential is it for your DH to finish his Ph.D before starting med school? Obviously it would be preferable, but if his goal is really to be a surgeon does the Ph.D. make a whole lot of difference? 2.5 years is a long time to put it off if he knows what he wants to do, though I guess if he hasn't applied this year then you are looking at 1.5 years before he would start anyway so maybe that makes sense. It might not be a bad idea for him to apply next year, though, and see where he gets in and whether any place might let him defer enrollment for a year. Then you could target your job search for where he is going to be.
For advice on managing academic job searches and dual body problems, Karen Kelsky at
www.theprofessorisin.com is AWESOME! She is kind of the like the female, career advice version of MMM. Not afraid of giving people facepunches, but also really supportive of people trying to figure out whether a life in academia is really what they want, and how to get there.
Re: where to put your money, a Roth sounds like a good option to me. You can withdraw your contributions at any time, so it functions more or less as an emergency fund. And it may be the case that those funds will not be used in calculating your expected financial contribution to your DH's med school costs -- that is the case for parental resources when it is a child going to school, not sure if it is the same for adults funding their own education.
One suggestion: budget more for travel to/from China to visit family, and be sure you are attentive to what your in-laws want/expect, especially if/when you have kids. While Chinese elders are pretty stoic about not seeing their kids/grandkids for long periods of time, it is definitely not a good thing not to go back regularly. Some of it depends on his relationship with his parents and other close family members, obviously. But in our case a HUGE part of our annual budget is travel -- four people times two transpacific trips a year and at least two-three trips to see his family as well adds up. But well worth the investment.
good luck working it out and building up your stash! DH and I managed to finish our Ph.Ds debt free and that was HUGE in terms of giving us a leg up on accumulating a nest egg, especially considering we started our post-PhD careers comparatively late (well, I was not so late at 30, but DH was 40). We don't have surgeon salaries and we are well on the way to early retirement after just over a decade of work at non-profit management jobs, so it can be done!