Don't waste your time on the head gasket and the studs.... Otherwise the plan is great. Upgrade the other stuff if it breaks, you won't hurt anything else if they go so no point in ripping the head off for no reason. You won't get to that point with your turbo so no need at all. With the water/meth you shouldn't have detonation so you won't need stronger head studs or a better gasket. Keep it simple and listen to people. The water/meth will take care of the shitty fuel and you can boost 18lbs on that turbo as long as the injectors don't top out which they shouldn't. Biggest thing is to not over think everything, just do it. For the price of the arp studs, which can be worse than stock, you can buy another de. I can't stress this enough, tune and keep it simple. No need to rip into a de for less than 400whp and even then for a street engine, still not worth it. What is worth it is a tuneable ecu and a water/meth kit to take care of the gas situation.
Drew