To answer your last question first, it would be very wise for you to consult a criminal defense attorney. The old urinating charge is a violation so would probably not show up. As this is your first possession charge, the court would likely go lightly on the case.
The notice of appeal is usually filed at the end of the trial, however, the appeals courts do grant later appeals. Prices for appeals and other legal work vary from attorney to attorney, and would be hard to state in this forum. Call a local attorney and discuss it with them.
You are doing drug court to presumbably avoid a felony conviction which will always be on your record as there is no expungement in New York State. Speak with your attorney about the pros and cons of continuing with drug court or taking it to trial. They know all the facts of your case and can give you advice on which way will work best for you.
This would be a family court issue as the student is underage. Searches of school lockers have been upheld by higher courts, so the search would probably stand at least given the facts that you have given us.
It would be very wise for you to obtain a criminal defense attorney given that there is some past history. It that was sealed it should not show up, however, you have a better at an ACD with an attorney.
It is likely that the drug charges will cause concern and you may be detained. However, you might also post this question in the AVVO immigration law section as many of those lawyers have a lot of experienced with these issues concerning criminal charges and immigration issues.
He should talk to his attorney about getting this hearing done quickly. However, the courts have been backed up due to storm conditions so this could be why. Tell his attorney should move to have this hearing done as soon as possible.
This is definitely theft and you should report it to the police immediately. Also you should activate the Find my Ipad function and also you might try calling it and see who answers. But definitely alert the police and also the school administration that this sort of thing is going on.