Talking from the other side of the fence, having been in a job that I loathed and loved with equal measure, and that demanded a lot of my time - ask hubby to do a cost/benefit on what he is currently doing, and take a close look at the family finances.
At the moment he's feeling pressure 4 ways
1/ Job - anything to do with the construction industry and you'll have to be exceptional every day to keep your job..
2/ DS
3/ family commitment/support
4/ HIMSELF - under estimate this one at your peril
We as a family decided that camping gave us a better holiday experience, and worked around switching supermarkets (which to date is saving us 25% of our old food bill per week), and clothes budgets - doing so opened up options, take a critical look at the 'cant do withouts' - see if there is some room to wriggle, especially if there is some stuff you can do yourselves.
This enabled the family to take some of the financial pressure off me - in ways that we could easily manage.
I would look into some workspace for him that isn't the dining table - small 'cabins' and plans are available.
tinyhouseblog.com/
for some ideas
When I was in a similar situation my world became polarised - into love and hate - and I hated anything that I needed to think about, or placed further dependancies on me, or was difficult and unpredictable. Quite often my DW would have 'dealt' with issues so that my DS's wouldn't take the sharp end of my tongue. As a team, we decided that there would be occasions where I would walk away from a situation, and simply say 'don't know', and she would pick things up.
The fact that he wants to be home with his family speaks volumes. he loves you all, and is completely unable to express it, excpet for this action.
If there is a way for you to be able to step back a little, so to give him some headspace, (beware the gentle reminders will aggravate greatly at this time!), then try to - as that is what he will need to be able to think straight, and do throw ideas in, to stimulate thinking about possibilities.
Most of all, keep the communications open, and try to make some precious 'you together' time.
I can say, been there, done that, and wouldn't go back if you paid me a million (well I might think about it for a moment, but the answer would still be no).
Oh, and after resigning my position after it all became totally unbearable, I am still decompressing - and thats 13 months ago.
Oh and talk to him about how he would feel if he 'lost' his job - this much internal pressure will be affecting his work performance, and could bring about that doomsday scenario, and he will not understand why, as in his eyes he will have been giving it everything and more - a surefire way to demolish self esteem.
I am the story of 'you too can get through this' - I have a smart and lovely DW, and a loving family to thank for that !
U