Check out the caresheet to correct your temps and get a digital thermometer/hygrometer to measure humidity and the temp on the glass directly above the heater. My immediate guess is that the tank is just way too big and he doesn't feel secure. Log hides don't provide security since you can see right into them (like a predator would). Try moving him back to his original tank (still check temps and humidity according to the caresheet), wait a week, and then try a rat similar in size to the mice, or slightly larger. I say larger because too young of a rat won't move as much as a mouse, which might not entice him to see it as prey, but not too much larger or it might intimidate him.
If you really want to put him in a larger tank, wait until he has switched to rats for a few feedings so you aren't changing more than one thing at a time, but he really doesn't need a 55gal (ever).
Clear as mud?
kk...will do.thanks for the advise. ill work on my skills on the web site. thanks for your patience as i stumbled through my posts...lol..