That is rough...idk do you have the ability like a spare room where he could stay for a bit if he needs to, like idk I think the best thin you could do is just remain a friend to him and see if you can help. But try not to be pushy as it may take a while for someone in such situation to really see the problem and if you push too hard they might default into just defending their partner, even if they are being treated badly...but they have gotten attached to it so idk I think the best thing is to let them know you care and if they can get the strength to leave.....it would be nice if as family you gave him a space he could stay in for a time at least till he can sort some things out.
Your not obligated to do all that or anything, it would just be a nice offer for your friend who is struggling and living in a camper to see if there is any way you can help him. Idk especially if his wife is abusing him and they have kids, like she is probably abusing them to.
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Tis the time to melt the Ice.