Agree the sulking is not a good immediate sign. Very difficult conundrum Zoo. Would you feel more supported with him there permanently (in which case that in turn may be a good thing for your and dc mh) or would you feel more depleted (not good for your or dc mental health)?
Even if you suggest him moving in on a temporary basis, it might not give you a true idea of how things may be in the future as he will be "on trial" ifyswim so not a true reflection.
Could you go out alone for a meal/coffee/walk/drive somewhere and discuss it without the dc around when you could share your concerns with him, and lay out your expectations, and discuss financial matters and also a plan B should it not work out (if a plan B is possible that is)?
If he isn't prepared to discuss it all openly and acknowledge his weaker points (which we all have) and agree to certain conditions without getting defensive or huffy then I think you have your answer. If he is willing to discuss however and continue to try seriously ... then ... you have a decision on your hands ... good luck with it! 
Or another suggestion is to judge it on a "gut" level. Do you still get a small "flip" in yr stomach (in a good way! 
) when you hear him come in the front door, or do you feel indifference/does your heart sink?
Having said that, I never thought I would say this, but love is not enough is it. You can love someone to death but if they are not committed, reliable, making a genuine effort etc, in action as well as words (to the best of their individual ability) it's no good imho. And particularly no good for the dc.
It also depends on your dynamic as well Zoo and whether you will still feel in control of your own home if he moved in permanently, or whether it's important for you to have time without him to recharge?
I know it is your own instinct to consider everyone else before yourself, but I think you should put your own wellbeing very much to the forefront on this point as you are the one that keeps the show on the road as it were.
Maybe one of the conditions could be to only agree on the basis that you as a couple have a weekly private assessment of how it is all going and that he would willingly move to plan B on your say so with immediate effect should you be having to revert to "parenting" him again or if he is draining you of energy and patience?
Bravo to Cagletini! Hope she sleeps well tonight Lane! Hope your dh feels better soon.
A very, very busy day but did have a long lunch with lovely friend in middle of it which kept me going! Too tired to write list but loads done especially loads of laundry. House moved on a lot in terms of tidying but Christmas still hasn't been banished entirely although nearly there. Determined to take dec boxes up to roof by end of this weekend. And to disperse piles of presents properly and check all thank you letters have been written.
Cherry waves to all fledglings! G'night all and have a good weekend!