In my experience Bass will eat about anything and everything. I have read you can get them to eat commercial feed, but it isnt always easy. Several hatcheries that produce bass have started them on commercial feed from the beginning, which would be ideal. I havent kept a bass, but with any fish I have found that variety is the key. Just because they will eat commercial feed I would still give them some live feed for nutrition and quality of life purposes.
Raising worms is cheap and easy, but a big bass needs lots of worms. Crickets and mealworms can also be "farmed" pretty easily and should both be readily accepted by your bass. Bluegill, or practically any kind of sunfish, would enjoy these as well. I would feed it these things, keep offering commercial food (the bluegill should eat it if the bass wont) and throw in some feeders once in a while. If you were serious about growing him out in a large tank I would consider breeding convicts or something to keep him fed.
As far as growth rates. Most North American Natives grow very quickly as in the wild it is dangerous to be a bait fish and predators need to grow large to open up new feeding opportunities.
