Trouble adjusting to new cage?

[Kitt]

Hello! I'm new here and I have a few questions about adjusting a bun-bun to a new home.
I got my rabbit a little over a week ago off of Craigslist. He's super sweet and adjusted pretty fast (I think, at least. I'm a first-time rabbit owner.) me and to his new home. I had him roaming free in my bathroom in the basement with the small dog cage I had gotten from his owner with the door kept open until I could get him a proper bunny house. Now that I have one, I have him out of the bathroom and into a big new cage out in the main part of my living space. I've had him in there for a few hours now, and he hasn't really moved at all. He's hopped around the bottom level a little but hasn't even investigated the other platforms. He's been thumping his unhappy back leg thump, and hasn't really eaten anything or drank anything since the move. I have his litterbox, food bowl, and chew toy from his old cage. I know it's a really big change for him and I know he's super stressed out. I guess my question is, what can I do to make the adjustment easier for him? Will he start to explore his other levels in the cage? I had his food and water on the second level originally but I moved them down to the first floor because I was afraid he wouldn't make it up there and I didn't want him to like, starve or anything.
My mom has cats, too, and they bothered him a little bit before I chased them away, so he's no doubt terrified of them, too. Will he eventually adjust or should I make other arrangements so that he's in a closed room away from them?
Sorry for packing so many questions into one post, and I hope I don't seem like a bad rabbit mommy :/

EDIT: This is the cage I built for him, if that helps. http://www.rabbitcondo.com/moredetails.htm

 

[tamsin]

Bunnies can get a bit upset with change, you have to remember for a rabbit their cage is their home so it's a bit upsetting to have it suddenly changed even if it's an upgrade.

He will adjust gradually but you can help by covering part of the cage (cardboard or an old towel) so it feels less exposed. Make sure he has something inside to hide in too, a cardboard box works well.

Putting everything on the bottom level is a good idea to start with, as it might take him awhile to explore upwards.

If you have old bedding/litter tray etc that will help in smell like home to him. If the old cage comes apart you could even put the base from it in there.

Do keep an eye that he does start eating again though as bunnies that get very stressed can go into stasis (their gut stops moving and they stop pooping/eating) and if that happens he needs a vet.

It really depends on him and the cats, you need to make sure they can't fit a paw through and poke at him. He may get used to them being in the same room but it won't work if they are constantly try to get him through the mesh.

 

[Kitt]

Ah, I did have a towel in the bottom of his old cage. It definitely made a difference. In the ten minutes after I put the towel in he started running around and sprawled out and started to groom and now he's eating. =D
Hm. They can definitely reach their angry little paws through there to bother him. My cat (the biggest jerk out of the bunch. He's the ex-boyfriend who made you pay for dinner and checked his reflection in puddles on the street on the walk home because he's hot stuff and he knows it.) is the only one who's really bothered him, at least. I think my mom's cats are afraid of him. I'm going to have to figure something out to keep them away from him.

 

[Nancy McClelland]

You can get a smaller mesh wire at a hardware store and cut it to fit.

 

[Kitt]

I ended up blocking off his area with a gate made out of my left over NIC pieces.