The general rule of thumb is that a dragon should be about sixteen inches long before you start using supers as part of their diet. The reasoning behind this is that prior to that there's a kink in their digestive system that makes them more prone to blockages from the supers' shells. He's pretty close to that size though, so as long as he's digesting them okay and pooping okay, I'm sure a few a day won't hurt him. I don't recall what the overall daily limit should be (its been a long time since I had a young dragon), but they are okay to use as a staple feeder, particularly if you still offer other bugs for variety - I switched my dragon to them from crickets once she was old/large enough and she loved them. Once your dragon is an adult you'll need to limit her to 25-30 supers a week because they are higher in fat than crickets (in comparison, she'd get 50 crickets per week as an adult if you stick with them instead).
Superworms are actually pretty easy to breed. If you're interested you could get started using the big worms from the batch you have. First you separate them out into one of those craft containers (the ones that are split up into small compartments, used for storing beads and stuff like that) - one worm per container, no food in there, but you do want some air holes in the lid (I used a small nail to melt holes in the containers I used). They will eventually curl up and begin to morph into what are called "aliens." The aliens don't eat, they just sort of sit there and their outer skin hardens. Then they split out of their skin as beetles. You put the beetles all together in a container with a substrate and some egg crates and the beetles will lay eggs which then hatch into teeny tiny superworms (the bedding will eventually look like it's moving). This is of course a simplified version of the process, but that's basically it - I don't like bugs and I was able to breed my supers without too much of a problem.
Hope this helps
Keep doing your research and do what works for you and your dragon.