Well good luck I had the same problem.
Ran hot all the time really ran hot pulling my boat.
Did all the things you have done with little to no help.
After all that I added a small transmission cooler in front of radiator and that helped but didn't fix the problem, added one inch of space between the radiator and the AC condenser (they were almost touching) that helped a lot finally added (I think it was called) Water Wetter to the radiator and that dropped the temp about 10 degrees. Still ran around 210/215 on a hot day but I could live with that.