Would he use a light box, like they use for SAD? Or there are fairly normal-looking desk lamps that use the same full-spectrum light that would be less noticeable for his office. And do you suppose he would give 5-htp a try? (5-hydroxytryptophan - a precursor to serotonin).
Also - could you get him to at least go to the doctor and get his thyroid and testosterone levels checked? Just in the interest of ruling out physical causes for his depression? (Maybe the doctor would be able to convince him to give anti-depressants a try if they don't find anything).
Meanwhile - I give you the same advice. You have got to switch his attention from OW to home by introducing novelty, flirting with him, sending him funny emails during the day so he has something else to think about and look forward to, introducing novelty into your life with him so he wonders what he'll find each night when he goes home.
