Hi two questions on your au:
One: how did Timmy accumulate all the "positive" magic for this to have happened?
Two: how does Timmy and others (Crocker, Vicky, The council, etc) respond to this? I'm looking more for the immediate response as we know later the trio have decided to stick together.
I note positive magic as he is a fairy not an anti, pixie, genie, or other magical being and the affects it had on those around them.
Constant interaction with magic has consequences, especially if he had been doing it for 58 years, it was impossible for this magic not to adhere to the child.
Timmy is a pure source of magic, as is his now innate power, as well as his ability to believe in it, which is a constant feedback loop.; His ability to desire, to believe that he can achieve something, gives him the ability to overwrite reality to his will in an alarming way.
That's why the boy was too dangerous, and everyone tries to keep Timmy hidden, so that what happened with Poof doesn't happen again.