If he insists on using the tube to sleep in and store I would take it off if you can and seal off for now. They can get chest problems with the warm musty atmousphere in a restricted area. Once he starts sleeping in his nest you can put them back. He is a typical baby.
He will pee in tubes, on his wheel, in bed! They never poop in the potty, just wee. Hammy poop is dry and harmless so dont worry if he does it all over the place
Ours usually do it in bed
