Hi,
Everyone seems to have the poop/ regurge question covered so I'm going to look at other things.
The security of the water bowl is almost certainly why your snake is using it. So if you want to alter where he spends his time you need to replicate that in the hot and cool end hides, depending on the size of the snake I have found plant pot saucers to be really good as low, tight, dark hides available in a range of sizes. Simply cut a hole they can enter through and sand away any rough edges.
You could, once you have hides they like, replace the waterbowl with something like a ceramic dog bowl they cannot fit under.
But I would add the more secure hides at either ends and make sure they use them before removing the current hide/ bowl to avoid problems.
Hope this helps.