A 20long can be a great tank for even a youngster...if you do it right. Here are a few suggestions:

-Cover BOTH sides. I see you have one side and the back covered, but not the other side.

-Place the thermometer closer to the ground. You need to know the temp where the snake spends its time.

-TWO hides, and not those half logs. Yes, if placed against a wall they can be seen as surrounding on all sides...BUT they aren't really snug because of the length. Better to get two small plastic bowls or flower pots and cut them down to size.

-Smaller water dish and placed in the middle of the tank. Ceramic cat dishes and small rodent dishes work wonderfully for smaller BPs.

-Add LOTS of greenery or crumpled paper in there! All that open space freaks them out.

-And get a lower climbing structure or turn that one on its side. Though some (I have two) seem to be good climbers and like it...what happens that inevitable time they fall? Make any climbing decor wide and low for their safety.

-To raise the humidity, treat the screen with foil and duct. I can send you a step-by-step pictorial I did on it if you like.

And yes, if the snake is roaming during the day or looking for a 'way out', its stressed because something isn't right in its home. Good luck!