But you shouldn't have loaded in the QNH? You need to use pressure altitude not pressure height for a density altitude calculation?
I have no idea what you mean by pressure height. There are a few ways to figure out pressure alt. If you are in the airplane you just set 1013 in the kohlsman and read PA on the altimeter. If you aren't in the airplane you can figure it out if you know the true altitude MSL, and the QNH. If the QNH is lower than 1013 your pressure alt will be higher than your true altitude and vice versa. So it is true that you need a pressure altitude of 5,500 at 49C in order to get 9,300 density altitude, but if you are sitting in an airplane at a 3,100 ft MSL runway and your altimeter reads 5,500 ft. with a setting of 1013 the current QNH would have to be about 0960.