I don’t think he was ever a billionaire, though he’s certainly done quite well for himself. Since leaving Apple, he has founded several new companies and projects, focusing a lot on education and philanthropy. He was also involved in founding the EFF.
He’s an engineer first and foremost, and several of his projects never achieved mainstream success, partly for being, IMHO, ahead of their time – for example, a programmable universal remote in the 80s, and a GPS-based item tracker in the early 2000s.
As far as I know, he has never been involved in any notable scandals.