Separation Anxiety

Hi everyone, 
I adopted a dog last Monday, and need some advice. He is a 9-12 month old (they think) Border Collie/Lab mix (we think) that we named Hank. He has a great temperament. He loves people, and is great with other dogs too. He's very smart and already answers to his name and sits and lays down for a treat. I know he will be a great dog when fully trained, but we have a few problems: he completely freaks out whenever I leave the house, and is not taking to crate training. 
I started with a metal crate, and he seemed scared when I took it out of the box. He wouldn't even go in when I put a high value treat inside. When I tried to crate him so he wouldn't destroy my home, he broke out in 2 minutes flat. I spoke to a dog trainer at Petsmart who suggested a plastic crate, so I exchanged for one. He did a little better and would go in when I put treats inside but was also able to break out of that crate in a very short time. I tested him while I was home and after training with treats to familiarize him with the crate.
I tried leaving him loose in the house because I had to go out for about an hour, and he pooped in the living room. I took him out several times before I left, so the problem wasn't that I left him alone too long. He didn't destroy anything, so I guess I got away easy on that one.
Should I continue with trying to crate train, or should I just give up? I'm thinking that he may have had some sort of bad experience being crated. I am not working right now and have time to work with him, but I don't want to cause more anxiety for him than necessary. I do need him to get used to the fact that there are times he will be alone, and I don't know what exactly to do since I feel like the crate training is not working. I am starting obedience classes with him on Wednesday, but I'm not sure this will help at all with the separation anxiety. Will that just get better with time as he adjusts to our home? 
I appreciate any tips or tricks. Thanks! 
Monica