You see that image above with the hairline crack in the coolant reserve bottle? That was enough to cause the to raise the temp of a M103 engine substantially - in very hot ambient temperatures - however I'm talking 115 degrees in the shad here not your ambient 85 degrees.

You have a new radiator even though off brand shouldn't have cracked up yet - even a real cheapie. The newer radiators have a stronger metal collar in the top radiator inlet to prevent cracking and break off.

Generally at ambient temperatures even with a little bit of coolant loss the airflow at speed and water circulation will keep the temperature down around ninety degrees. When the car is slowed and the airflow reduces then the engine heats up.
Your engine is up around 105 degrees at highway speeds at ambient 85 degrees. There is some serious problem there.

I.M.H.O. you cant screw around here you need this problem looked at before much more expensive damage possibly occurs.