I sympathize as I have been through similar -- DH was unemployed for best part of 18 months until about a year ago and appallingly depressed about it. We didnt have children at the time but there were other stress factors involved like us having a huge debt pile and living in a foreign country. It was pretty rough and put a huge, though thankfully temporary, strain on our marriage.
Ultimately the thing which snapped my DH out of it was finding work, initially part time and then more recently a really nice full time job. But I agree that you have to walk on eggshells all the time with depression -- on the one hand you want to show sympathy, not criticize or nag but on the other hand depression causes people to be very self-centred and get into negative patterns and you want to jolt them out of it and get them to stop dwelling on negatives.
If I can offer two pieces of advice they would be these: a) try not to criticize him personally for not having a job -- it's immensely undermining, particularly for a man, even if done with good intentions. Try to frame everything in constructive ways: let me help you do this, rather than why don't you do that, etc. Not easy, particularly when you've borne the brunt of a rant, and the sleeping all day thing is very unproductive, but framing it this way helps him remember you're not the enemy. At this point he may feel very isolated and you may be the only friend he has.
Also, get him to a GP, even if its done by stealth. Getting a second opinion will a) bring home to him that he is actually depressed and that its noticeable to others and therefore probably having a significant effect on his family and b) the GP may be able to offer practical advice for dealing with the stress. But the first thing is key -- in my experience men tend to go into denial mode about depression and think they can handle everything on their own or with their spouse. Having a professional third party tell them otherwise will force them to confront it.
Good luck and remember it will pass.