Progress! Good, I'm glad I didn't send you on a goose chase!
Does turning the AC on and off bump the idle up now? (make sure the defroster is off..)
With everything turned off (headlights, heat/AC, rear defroster, radio, etc), and your hands off the wheel, Is the idle steady but high, or does it fluctuate?
Trying to set the idle speed without a steady idle is a study in frustration.... You need to get the idle stable first.
Speedy's suggestions in that link should help.
If you do decide to try adjusting the idle screw be aware that the rubber "O" ring that seals it is over 30 years old now and is probably hard as a rock.
Turning the screw may crack it, causing a leak and making things worse.
The only place I know of that sells new ones is 3SX
The world's oldest and largest 3000GT and Dodge Stealth Source for Performance, Maintenance, and Service
I try not to mess with that screw unless I'm sure it's necessary....