1. You have both a legal and an ethical obligation to tell the truth, and it's never to late to do that.
2. It is possible the police would charge you with false informing, but I think they would be more interested in the truth. Be prepared, however, not to be believed. Many women recant their testimony regarding violence against them even when true. Since he's already been convicted, it won't be easy to undo, especially since he plead guilty.
3. You may also ask to talk with the prosecutor on your boyfriend's case.
4. He is a dufus if all he had to do was attend those classes, versus now where he will spend some time in jail regardless. In the meantime he should consider apologizing to the judge and agreeing to go back to classes He needs to talk to his attorney both about the probation violation and about your willingness to recant.