I don't envy you, my wife has bouts of depression and used to take some drug (cipralex) but wasn't happy about taking them - no pun intended. Now she wakes up early and uses a light box during the darker winter months - I'm guessing they don't really happen in Texas (but could be wrong). Also she's taken up running - more of a jog really - but she's stuck with it and the combinations of being outside and getting exercise seems to have improved things for us. Don't get me wrong, she still suffers on occasion but it has vastly improved things.
She also sought help from a Mental Health charity, and they gave her a very good book called -
Living with a Black Dog, it's basic but I found it quite helpful to
begin to
try to understand.
Regarding splitting up, it's a tough one to decide - I guess (but wouldn't like to be quoted) that when it really starts to be detrimental to you and your work that a separation may be a good idea - but that really is your decision, and you say you want it to work. The things we put up with for nice T&A
Good luck to you both.