Snakes generally poop once a week. Mine usually poop after they get their next meal, others a little before.
As far as the shed goes, cover 3/4 of the screen lid with a towel. That will increase humidity. Soaking (letting them be in water) is done after the shed was unsuccessful. It's to help get the stuck shed off. Use tepid water and fill it to about half way up the BPs side, get a towel wet in the same water and put it in there as well. They will use the towel to slither on and help the shed come off. Let them stay in the water for about 30min.