It sure sounds like a Regal. The only other possibility would be desert HL, but not likely.
The heat pad won't cut the mustard if you want to keep him alive very long.
You don't want to put that little tank out in the sun because it will become a little oven and cook him. Best thing to do is get you at least a 20 gallon tank (and this won't be enough when he gets big) and get a good UV lamp of about 100 watts.

He probably isn't eating because of the setup you have. It's just too small and not right yet.

Did you do some reading?

It might be best for the little guy if you release him back where you found him.
But if you are sure you want to keep him you'll need to get the right setup for him.
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