The first thing you need to is how Pennsylvania law applies to your case. Not how other jurisdictions handle their violations. In Pennsylvania a parole violation on a county sentence could land you in jail for the remainder of your sentence. For example, if your original sentence was 90 days to five years and the supervision was kept at the county level you could spend the next four years and nine months in jail. If you were sentenced to a state prison then there are presumptive ranges for...
What you should do is contact the person who is supervising you and ask them if they will accept the classes you do in PA but before you do that contact probation in your home county and get them to provide you with a printout if their requirements so when you contact Virginia you have the information ready for them.
That will not invalidate the warrant. What is important though is when the charges were filed and did the police use due diligence in finding you. This area of the law is very fact specific but if due diligence was not shown and you did not do anything to hinder the police finding you there is a chance the charges can be dismissed.
You are absolutely correct that DAs think all DUI cases are the same. That is why when someone is charged with a DUI they need a lawyer who specializes in defending them using science as well as the law.
They have 365 days from the time the complaint is filed. If the defendant causes a delay or asks for a continuance the clock stops for that time. Your lawyer should file a motion to dismiss based on Rule 600 but not file it until the 366th day. That way the DA doesn't have time to get you on the trial list or pull some tricks to say it isn't their fault.
Generally speaking when a juvenile has no prior record the disposition is either a consent decree which allows for the expungment of your record to an adjudication which is equal to guilty followed by supervision whose length is determined by the juvenile probation officer.