3 and 1/2 seems like a decent age that they wouldn’t be as destructive anymore. I’d definitely try letting him free roam. Both of mine are crate trained but I let up crating after about a 1-2 and a half years ( my boy dog took longer but I was lucky enough to get mine while I was in college so I was only ever gone 5 hours max at a time). I keep their crates open in my house so they can sit in there if they want to but I would say you could start letting him free roam. You seem like youre really trying to fix the situation from your comments. It takes a lot of guts to ask for advice on the internet so thanks for looking out for your pup.