It would be impossible to answer the question without having a lot more facts about the charges, his prior record and his original sentence. Obviously he needs a criminal defense attorney to help him mitigate the outcome.
There are several factors to consider in resentencing. You have not provided sufficient information to allow attorneys to comment on a sentence with insight.
Difficult to say. One big issue is whether he had 11 1/2 to 23 (which you may be referring to as 2 years or if he had an actual 2 year sentence, which then bumps it up to a state sentence. He definitely would be required to serve any back time. He would not be able to be re-sentenced on a parole violation and therefore he would only serve the parole back time. However, because he has the probation tail, that can be revoked and create a much more complicated situation. He could be re-sentenced to a new sentence on the probation violation. That's the true danger.
This is not intended as individual legal advice and there is no attorney client relationship established by this answer. It is advisable that you seek individualized legal assistance. This is not a substitute for hiring an attorney.
attorneys need more information to answer this as stated. is this state parole or a county sentence? how serious are his new charges-did he commit another retail or kill someone? it is always possible that he may be sentenced by the parole/probation judge to the balance of his sentence.