It's really too bad. I'm glad he's with someone who actually cares enough to take the time to figure this stuff out. A lot of dogs who haven't been rehomed don't even have that, so you should feel good.
I personally would not leave the house without MY dog in a crate, but I understand why you're doing it with this dog for now. Over time you can just randomly leave the crate open and leave treats in there. He'll be OK with it again and then you can start using it. When used correctly, they really do like it.
Thanks for taking care of this dog. I got mine as a puppy but it was kind of the same thing. His human parents weren't responsible, although they are good people, and let their dogs have puppies. They still haven't neutered them and I've offered to pay for it, find a charity to do it for free, everything. I got Kody as a "gift" which was a blessing as I needed it in my life, but it was definitely not the greatest way to go about things.
I have been through a lot, and started my web site because I knew other dog owners were probably frustrated too, and the ones who care can learn to live happily with their dogs.