Your stubbornness is part of your problem. drilling holes should never be done.
Use a temperature gun on your temperature sending unit where it screws in the block to see if your gauge is showing the correct temperature.
I had the same problem. put in high performance water pump, a 3 core Champion Radiator plus new temp sending unit, took out the electric fans and went from 200-220 to a solid 190 at any speed. a shroud and the mechanical fan are part of the equation.
