Glad to hear he is keeping the small meal down. Stick with small thawed pinks until the snake is keeping all meals down.

Backwards eating is no problem. Happens alot.

Kings/milks regurge when stressed from shipping, too cold and/or dehydrated. Shipping seems to cause dehydration and stress. I recommend a humid hide in the cage if keeping with a glass tank and screen top. Humid hide is a plastic container with sphagnum moss damp in it. Cut an access hole in lid, or even just leave the lid off. Any food storage container will work.