Join Date: Oct 2010
Location: Victoria, Australia
It's probably just what tends to be referred to in the hobby as a 'protein film', which is harmless, but unsightly. It tends to happen in tanks with very low surface agitation. You can manually remove it with a piece of paper towel. Increasing the surface agitation in your tank should break it up. Sponge filters are good at this, as they agitate the surface, but are still gentle enough that they won't blow your betta around the tank.
In regards to the pellets. It may be that he doesn't like that particular brand or variety. I've found some pellets are much harder than others, and my fish have struggled with them. Time and patience tends to be all that is needed to get a fish accepting pellets. A healthy fish won't starve if you withhold food for few days, and if it's hungry, it's more likely to accept food that it previously refused.
What sort of worms are you feeding? I assume bloodworms? If so, I'd prefer to feed my fish frozen over freeze-dried. Frozen seems to cause less problems with bloating.
Good luck with your newest betta. I've lost a more fish than I care to admit through ignorance and inexperience. This hobby can be a very steep learning curve.