I’ve had it twice. The first time it went undiagnosed for a year, the second I began treatment before diagnosis.
It’s had major impacts on our marriage, but some of that was also due to the very real adjustments we had to make having a baby. That shift exposed some major weaknesses both of us had.
One thing women sometimes say to each other is that hormonal changes just amplify everyday irritations. I know it can drive me crazy when my husband is dismissive of things that bother me because “it’s just hormones.” Well, no, actually, the things he’s doing (or not doing) always bug me, but I can cope better/set it aside when I’m not in hormone crazyland. That’s not to blame him for my issues, but it goes a long way when instead he’s sensitive to those things, and maybe moreso when he knows it’s harder for me to deal.
ETA: Sounds like your situation is very unusual too, which just adds stressors all around. I think it can be wise to do research (but real research, don’t rely only on anecdotes like here) but the basic advice is always the same in marriage - love your wife.
Men sometimes experience depression after birth, too, because the adjustment is really severe. Being apart is probably very hard on you, even if you’re not dealing with sleeplessness and other factors.
Counseling could be very beneficial in this situation.