Yes, if you are arrested and convicted for another offense while on parole it would be a parole violation.
Yes, he could be. Sometimes parolees are saved by their relationship with their PO so he should report the offense immediately.
He needs counsel and he needs to report to his PO. And it does have to do with his restrictions. It is pretty much a universal condition of being on probation/parole that one engage in no unlawful conduct.
Drinking and driving is engaging in unlawful conduct.