clutch fan

Idles @1200 rpm , won't go lower .

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There's the main reason for your hot running engine. It's struggling and 'working' right from the get-go.
Tap or wiggle on the secondary throttle shaft. Most likely it's being held open just a tad (or by a screw).

With only 7° initial it should also run like a wet newspaper, not helping keeping an engine cool at all.
Use vacuum-advance.

Rust in the cooling system is making it less efficient by a mile.
Consider soaking/treating the entire system with a mild acid-solution to dissolve the rust. Flush well afterwards.
I've used citric acid with good results. Rust turns into white/milky sediment which can be flushed out later.