Theres a few things, "Those coco bricks" use them and toss that carpet, it holds mold/bacteria IMO!

As for feeding do this!

1) Go in in the dark as to not casue too much distruption
2) Buy black paint/paper and black out the 2 sides and back of the tank ( I used that plasti dip stuff when i had my tank)
3) Just leave the mouse on the warm side! over night it should be gone, My lavender spider girl never has or will take off tongs, she whacks it over n over but unless i drop in and close tub she wont eat!
4) He could just be fasting/thinking its time to breed aslong as his weight loss isnt anything huge, just let him relax, hell eat again if everything is done properly.