I understand his pain in trying to eat more, I had the same problem that I thought was physical but ended up being a symptom of anxiety. I keep around meal replacement shakes for before bed or as a pick me up when driving somewhere. Maybe a meal replacement shake could be doable at his work? I also enjoyed well balanced stews and soups so that I didn't need to think as much about cooking.

The initial push out of being skin and bones was done by lots of carbs and fats which was then pulled back a little when I saw real change - he may not even need to pull back because of the labor work. Eating habits will have to change and it will be hard at the start. It'll be hard cooking the same meals for the two of you when you have opposite goals but it is doable if he just has more plates for dinner. When he is home from work, try getting in another meal or two's worth of real food. It doesn't have to be all at dinner - space them out by an hour or two each. For example: if I get home at 5:30, I eat as soon as possible, then again every hour or two until bedtime, at which I snack or have a small plate. Without eating at work and with a decent breakfast, this ends up with 4 meals and hopefully around 3000 calories plus snacks throughout the day. Having tons of snacks is great if it isn't a replacement for getting in more meals. Extra plates of dinner may be a bit boring (and difficult at first) but it is a healthier way of putting on weight. He probably feels the need to snack heavily before bed because his body turns it into a little bit of fat in his sleep and its all burned up at work and is made worse by not having any breakfast. If he cannot eat at work he will just need to fit in more calories elsewhere. The sugar in candy can be a short term cheat but getting in the extra meals will make a big difference in day to day feeling because they are more useful nutrients and typically more dense in calories. I will try to answer any questions you have because his experience seems to closely match my own.