Yep, your Tstat is clearly working perfectly! But you're generating too much heat at idle for the passive cooling of the setup. My truck is the same with the thick radiator, there is no airflow without the fan...
This is exactly how the first car's cooling system worked. Never overheated, but with everything crammed in such a small space and thick stack, the temp rose to fan trigger quickly in the summer heat when the car stopped moving.
Your warm up curve needs to end by about 75C to not be enriching when the tstat is open which we must deem as "warm enough".
That makes perfect sense.
Your idle is a tiny bit high at a bit over 1k, but I guess that's on purpose to assist with cold running, right? Cold right now of 28C and you have what appears to be unassisted 1070 RPM.
This ford throttle body came to me with a large hole in the throttle plate. Apparently this hole is typical for base idle and changes in size depending on which model car the throttle body comes in. This hole put my idle at nearly 2000 rpm fully closed. There was no removing the screws without grinding the ends off them- they looked pressed on the ends. I brazed the hole shut which dropped the idle to where it is now. But in the process there was enough heat to slightly warp the plate, so there's a throttle leak around body lip/flange when shut. If little pressure is applied to the plate it seal enough to where the engine will pull the idle valve open.
Lowering the RPM and getting back to stoich should make it a bit happier and cooler. Pull the warm up curve back just a little more, 100% by 75C (or lower if you want/can, sooner into stoich idle, the better, really, only add fuel where necessary to run acceptably)
I need to pick up another throttle body without a hole in it. They're dirt cheap since they came in so many different fords- typically around $25 delivered.