Wow, Josie -- he's looking SO much better already! Yes, the proper lighting will do wonders, he'll "color-up", and he'll FEEL better about himself! Without proper UVB, his body cannot make the D3 vitamin, which helps him properly digest his food. Temps do that, too -- without proper basking temps, his little body just won't work properly.
Have you tried giving him superworms yet? That was the main live-feeder we used to nurse Xena to health, she was skinny when we rescued her, and proper lights, food, vitamins, heat & LOTS of love & patience were the keys for her getting healthy. Now we have a nice little piggy on our hands... She's still skittish with our two youngest humans (9 & 10) but she's coming around. Now Xena is healthy and eating hornworms (very high in calcium) and superworms and multiple bowls of mustard & collard greens/butternut squash per day (her favorites)
Keep up the good work, it looks like he forgives you for your mis-knowledge!