I agree with Crazymonkee!

No food = no poop, no need for warm spot to digest, no growth, and no shed
(obviously still a NEED for the warm side, but just that your snake isn't using it as you said).
I think all of those changes are consistent with your snake refusing food.

I struggle with the humidity for mine as well. We have a mini humidifer that we got from Wal-Mart for about $20-$40 situation beside the glass tank for the winter, when it gets really dry. You can always switch to different substrate to hold humidity better (sorry, I forget which is best for this, as I use aspen right now - and should also switch). I mist a few times a day as well. You can also have a shed box filled with damp sphagnum moss, as said above. I really like that because the moss is cheap and expands like 5-10 times its original size, and lasts a long time!!

Good luck and just keep trying with the food!