I am a med student (and a future surgical resident) so my asnwers are from my surgical rotations, etc.
It really is not that bad, and you'll be fine! Really!
My husband is a research scientist, and also works long hours that change (on his whim, not a patient's.) From his perspective, he misses me when I am gone long periods, especially overnight, but otherwise I see him for dinner every evening and we spend quality time every weekend. We volunteer together and see friends together and apart, etc.
He usually is asleep when I leave in the am, but I would love him to have breakfast with me.
Based on my experiences:
-I suggest trying to follow your SOs sleep schedule if possible,so you can "do" mornings and bed times (you can always nap later!)
-Try to have things for you to do during the day while your SO is gone so you don't feel bored or reesentful. It is nice to help keep the house functioning, but you should have "you" stuff too that you do, not just do what needs to be done because you are "available." (If these things overlap, great!)
-Try to have patience when your SO must stay late to take car of things at the hospital. He might not be able to call right away, but when he does, he should be apologetic, and you should be forgiving.
-Something I heard from a surgeon-internist couple: during their residency, they paged a "secret code" to each other to say "hi!" or "I love you!" (like 222 or something)- just makes sure it isn't embarassing because the nurses or scrub techs will read his pages outloud when he is scrubbed in!
-Sometimes plans will change at the last minute, or holidays will be on the day after the actual date. It sucks, but it aslo isn't a big deal. Enjoy your time together and if it starts bothering you, let your SO know! Don't let resentment build.
All in all, based on my expeirence, I don't think you'll have any toruble. Don't worry that you will divorce becuase of the residnecy. I think you won't divorce at all, but if you do, it'll be typical stuff- kids, money, etc. You sound very understanding and very willing to work on your relationship, so you'll be fine!
I am really happy in mine!
(Just got off work, he's not back yet, but he is picking up food and then we wil watch House before I crash!)
hope this helps!