I would move him to a shoebox sized tub until he starts eating. It's honestly your best bet in my opinion. Otherwise crumple up a bunch of newspaper and fill the tank with it. He'll feel much more secure with less space. Also, make sure your hide is really small so that he has to ball up to fit inside of it.
I'm assuming you have a heat pad as your heat source you can just put that right under the tub. Also, put a towel over the tub so that it's dark inside and secure. You can leave a pinky in overnight if you have to, they can't chew on your snake. Otherwise you might have to start assist feeding.