Hey there Jason...
Please don't think I'm getting annoyed by your questions... I'm actually here to answer these types of questions for you. So... you can keep them coming!
Per-diem is different depending on each pilot groups negotiated contract. Ours states that you do get per-diem for every single hour you are on your trip. That includes overnight, while flying, while eating, etc...
It is not taxed... unless you are in your own base. So... if you get an overnight in your home base in the middle of a trip (which is inusual) then that per-diem is taxed.
Deadhead pay is a type of "soft time". Soft time is time that you get paid for without actually working. Deadheading is when the company relocates a crew to a new city in order to either start or continue a trip. Deadhead crews sit in the passenger seats too, and pay is again determined by your negotiated contract. At XJT... we get 100% deadhead pay... in other words... we get paid our normal flight time rate for the flight time of the deadhead flight. Some airlines only pay 50%, some more, some less... again... it depends on what you can negotiate.
Bob