Check with the department to find out if the petition was approved. During semester breaks and holidays, extra hours are possible for all students, but they must be petitioned, too. Dates change every semester, so check with departmental offices. Graduate assistants must be appointed for at least half a semester to get the non-resident fees waived. The cut off dates are on or before March 1st for spring, July 1st for summer, and October 1st for fall.
Stipends vary widely among departments.
The minimum amount a graduate assistant can be paid per semester is established by PS 21. There is no maximum amount. Your department is required to put your stipend amount in your assistantship contract, so contact them for more details. Your department can tell you exactly when you'll get paid. I am being charged nonresident fees, but I am a graduate assistant.