Honestly your frog doesn't look like he wasn't eating for 4 months, may be its the pic. Crickets may help, he was probably used to eating them in a store.
You know given he was down for so long and survived I'd do electrolyte bath to help restore a proper balance and get reptiboost ( fluckers reptiaid) and dust all your food in it for a week or so.
The bath should be warm (80-82F), and ratio as was suggested 1 part of electrolyte solution ( unflavoured pedialyte or similar) and 10 parts of water. 20 min.

Yes, regular ambient light is fine. i very strongly suggest you get a digital combo instead of your gauges. Analog ones can show whatever they feel like it. This way you be sure of temp and humidity.