IR guns, no matter how good only give a reading for a particular spot on outside of tire. Tire surface temperature can vary by well over 50F.
I have used $10,000 IR camera and have seen the facts. The surface temp can also be 50F below the hot spot in the tire which in about 1/2" to 3/8" inside the shoulder of the tire.
Increase of pressure is a VERY strong indication of weight unbalance.
TT should have at least a 15% load capacity margin between static individual tire load measurement and tire load capacity on the heaviest loaded tire.
TT should also run the inflation on the sidewall of the tire to keep Interply Shear as low as possible.