I never got the sandbox parts to work but I was able to create my own Tezos chain. I downloaded the source code, then changed the dictators public key to a key that I controlled. Then, after compiling and running the node, I could inject the protocol with my dictator's secret key:
tezos-client activate protocol Ps9mPmXaRzmzk35gbAYNCAw6UXdE2qoABTHbN2oEEc1qM7CwT9P with fitness 24 and key dictator and parameters ../mysandbox.json
After that I could do whatever I wanted with the bootstrap accounts I had in my JSON, bake, transfer, make new accounts, etc.
But now I can no longer bake. The protocol injection succeeds:
But tezos-client doesnt have the bake option anymore when I'm doing all this from scratch now.