Need weight GAINING help.

First of all, Hi! I'm a long time fitnessblender lover - but this is my first post!

I *wish* it was about me, lol, but it's for my husband (I need to lose about 30lbs - workin' on it!).

My husband is about 5'6.5" and weighs 134lbs. He doesn't work out anymore because he works at a mill 48 hours a week, manually stacking wood pretty much the whole time and he's (mostly) all muscle from that. He has lost a TON of weight since working there, and let's say I'm feeling lazy and let him do all his own cooking (typically I love meal planning...but sometimes, not so much), he will literally lose at LEAST 5lbs in a week.

He wants to gain probably about 10lbs, but we're not sure how to go about it. From doing him BMR + activity level, I gather he will need around 3,200 calories to gain 1lb/week - and we want to do that in a HEALTHY way, but usually my healthy meals are naturally low cal, and you'd have to eat a ton to get a good amount of calories - and his appetite isn't that great.

I already have 1 idea (a peanut butter banana smoothie to the tune of approx. 600 cals!), but we need more ideas.

And would working out help? He enjoys lifting weights and such (though he's usually too tired), but he doesn't want to rev up his metabolism even more, losing more weight. (Man - I wish I had this problem!!)

Also - our funds our pretty limited...

If anyone read this thanks in advance!