Dear Forgotten Father,
The behavior you describe is not that of bi-polar but more so of an adjustment or conduct disorder. However, since you are not with your son full time, there may be other behaviors you aren't seeing. Certainly, bi-polar and probation don't go together.
SOunds to me like a 13 y.o. out of control. What is the home environment like. Sounds like the 13 y.o. is trying to get out of the house, grab attention, or in some other way make a statement. If you have just recently learned of his existence, he too, may be struggling with the idea of new family, new roles, etc. The distance may be a problem. Do everything you can to have frequent phone or email contacts. Find out what that mind is thinking and searching for. I have a feeling, you aren't being clued in on the entire picture.
Open communication with the schools and probation dept. if possible. Put yourself out there as a willing part of the solution.
Dr. D