It sounds like he's doing what Balls do. A lot of them tend to roam around a LOT at night. The tank size should be fine for a year or two depending on how fast he grows.

Oh, and it's not too uncommon to get bit at night, especially right after dark. That's typically the time they stick their head out of the hide and wait for a meal to come by.

It sounds like he's in a great setup, though. Looks like you did your homework.