That sounds just like Buddy was when I got him! He had been living in an old barn by himself, they didn't know how long he was there, he was only a year old at the time.
When I brought him home he wouldn't leave his crate except to eat and potty (like you said) little by little, he would get more and more brave. Walk a little further into the living room when we were watching TV. But when ever one of us would get up, he'd run back into him crate. I spent every second I could sitting next to his crate, talking to him, giving him treats anything and everything I could to win him over (I also slept next to his crate the first 2 nights he was at my house)

I would lay down right in front of his crate with the door open and talk to him for hours. I can't remember how long it took before he was better, (well... he's still afraid of my hubby, but he's the only person he's still THAT afraid of... I think it has more to do with Buddy wanting to protect me from him)

Buddy was the same way.... wouldn't only get close enough to take a treat and keep on running, it just takes time! And even if I'd told you that it took 6 months for him to come around, every dog is different, so you never know how long it will take!!

Good Luck, and don't give up!! I've had Buddy now for 13 months and I'm still not giving up on him ...... praying one day he will like my hubby and we all can live a "normal" life!!