Those sound like good healthy greens. You might want to think about sprinkling a few pieces of cilantro over the top, the smell seems to entice them. Have you ever tried collard, escarole, endive or dandelions? Those are real favorites here. You could also put a few slivers of apple, grape, melon, etc on the top too, the different colors might interest him.
One of my tanks is the same size as yours and I'm using a standard 60 watt household bulb on the basking side with a hollowed out log about 10" away and then on the cool side, I have a 25 watt bulb. I'm getting temps of 102 and 80. What brand digital with probe are you using? Do you lay the probe end so that it is touching the basking spot then wait about 45 min for the temp to stop rising before getting the final reading? Is the basking bulb a white or colored bulb? Is the UVB a coil or strip fluorescent bulb?