Stu, grab the fan that Scatpk offered. Find the stock style fan that fits the shroud the best. It'll do all you need. Chances are that flex fan is flattening out too much at idle and not pulling air.
For most cars the stock style cooling fan works great.

Forget the pusher fan. It will restrict air flow on the highway. I ran an electric 18" pusher on the hot rod. The temps went up about 10 degrees on the highway with it running. The electric motor could not spin fast enough to keep up with 60 mph air. That turned it into a wind powered generator.
With the pusher turned off the temps were still higher at speed than without the fan.

Your problem is air flow from the fan. Put the right fan on the car and it should fix it. Best of all, it'll be free (or a beer in exchange).

We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon