I'd bet if you put one of these on your low RPM creep will disappear:
These are called RV fans, and are intended to move a ton of air at low engine speeds, they do just exactly that. At idle you can feel how strong the suction is in front of the radiator by standing there.
My radiator shop guy showed me with cigarette smoke how little air the clutch fan was moving at idle. At that time in the late 70s the fans were under $20, so I said I'm going to try one. It one of the best cooling moves I ever made. The prices have doubled since then, $29.99 but still a good buy. The largest they make is 18 inch, but it still works better than any 19/19.5 fan I've tried.
https://www.summitracing.com/parts/aaf-all30095
The difference between this fan, and a conventional fan is the almost 90 degree pitch on the fan blades, that's what allows it's ability to move air at low RPM.