What is the brand name of the UVB bulb? Reptisun 5.0, which looks like a florescent light, is the most common brand out there. How far above the basking spot is it?
If you can, you might want to give him some time outside in a Rubbermaid container. Since he's still so small, make sure it's supervised time. Even half an hour a day could help that soft spot near his tail. Leave the cuttlebone in the tank even if he doesn't eat it now. He might decide to eat it later. You might consider adding some dark leafy greens to see if he'll nibble on those. Just make sure to remove the hard back before putting it in the water. I also like salmon pellets, but I've only seen them for sale at reptile shows.
Katrina