If automatic, do you have a transmission cooler external to that on the radiator? An auto trans dumps a lot of heat into the cooling system.

Flex fans move LESS air at higher engine speeds. But that's not generally an issue, as the movement of air through the grill scavenges the radiator's heat.

Never stops climbing is bad. 180-190 is great, peaks to 210 are common.

I would suspect some sort of water restriction in your cooling system, whether it's a lower hose that collapses partially when running at speed, or a radiator core that is partially clogged.