Hiya. I am unfortunately that DH (very small d) who suffers from depression and anxiety.
I think the best thing you can do is tell him (when he is not tired and liable to snap your head off) and if possible without losing your grip on your emotions, that his behaviour is having an impact on you and the family and that keeping up your happy mum veneer and keeping the house going is exhausting. My DW did this to me and it hit home, not immediately as I was defensive and all "ah so that's my fault to is it?" at the time, but afterwards I realised what a serious pita I was to live with and that I could at least try to help around the house or realise that my actions had an impact on others.
Sounds obvious that a depressed person makes those around them down, but they can be so inward focused and "woe is me", that they forget about the rest of the world. Be careful though as you dont want him tipping over into "so you'd all be better off without me" territory. Make it clear you love and need him and would not be better off without him, but let him know it is having an impact and that you are human too.
Then suggest he gets help. I have PERSONALLY never had any success with anti-depressants and they have made me worse. But they work for some people and its an option. I have gone to the NHS AIPT website and self referred for therapy. Its a long waiting time (6 months plus), but I've found their support to be really good. In the meantime, I would advise he looks at something like Full Catastrophe Living or tries an MBSR course or the pair of you talk. I know its easier said than done that last bit when you're speaking to a bear with a sore head, but it helps.
Try and figure out what his triggers are - or more to the point try and get him to do so. Is it work? Drink? Lack of sleep? Age and how he looks / feels? Sex? Money? The world? Whatever?
For me, I quit drinking. I quit reading the news. I'm trying to sleep and exercise (hard to exercise when you feel tired and fed up). I have money worries and a tough job and my reflection looks so damned old and I don't remember what sex is, but I'll deal with those afterwards. I am on an IAPT course for Emotional Regulation and following that, I'll be on a course for Anxiety. Those help. The MBSR course I did helped a huge amount, but I need to get back into it.
I wish you luck and I will try and respond if you wish. I just wanted to try and help, as I feel so sad about what the miserable b*stard that I can be does to my always smiling wife and I have seen the cracks in her facade and I understand what a weight I am to drag around and I am working to get back to the old me. We both want it.
PS. Little notes and kindnesses from my wife when I didn't deserve it really helped me. They made me keep on loving her and eventually get around to thinking "maybe I should do something in return". I tend to repay her in DIY. I fix things and try and make the house nicer for us and do chores. When I am at my worst, I withdraw and apologise and say that its not them, its me and I will try and be back as soon as I can.