Ok 1st thing, a 55 gal is wayyyyyy to big for one that size, he needs a smaller place so I would continue to use the 10 gal (or divide the 55 gal into a smaller section) till he gets bigger. As for the water, I wouldn't even make it hold that much, that's a LOT of water, the whole waterfall thing def sounds awesome, but he only needs to be able to drink water really. If you cover the top 3/4 of the way with tin foil it seems to hold humidity much better.
As for the heat question on bedding, the acurite thermometer can help you tell what the temp is over the UTH with the probe, which I suggest you hot glue in there because I tried with the little sticky pad and it comes off very easily once the humidity gets to it.
For hides, check out reptile basics, they have safe plastic hides of different sizes for all ages of bps. They are super easy to clean and after shipping cost a lot less than anything you will find in a pet store. Also, double entrance hides are not ideal for balls as they need to feel secure, while heat go in the tube, it's most likely just because that's the only safe feeling area in his home to him.
Hope I have given you some helpful info here!
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