This is wonderful news!
If you can add some probiotics and nutritional yeast to his diet, once bad bacteria has been cleared out it’s best to occupy all that free real estate with good bacteria so something nasty doesn’t take up residency.
Is a vet an option?
Two things jump to mind with what you described, the first being a serious respiratory illness, the second a serious gastrointestinal issue, an obstruction, parasite, or infection causing malnutrition and a swollen lower intestine.
It does look like the lower jaw is broken. If it was just a crack in the keratin it wouldn’t be much to worry about but the crack that travels down the jawbone you’re right to worry about.
I wish I could give advice but I haven’t seen something this severe, I think it’s best to have a vet clean...
That looks like it may be a tendon issue. You can try to splint it, the sooner you do the better the prognosis but sometimes in many cases it doesn’t work out so it’s best to prepare yourself for that possibility.
This has better information...
In general geese don’t like to be in confined places, they instinctually prefer wide open spaces where they can see predators coming from a distance, that’s probably their main gripe.
unfortunately for them they are better off in a secure place after dark. It’ll be a chore but you’ll just have...
Can any critters get in the barn? If they saw something spooky in there they’ll definitely be afraid.
Another possibility is rain, has it rained recently? The sound of anything pinging off the roof can be terrifying to geese.
Whatever the issue is consistency is your friend with geese, doing...