I haven't taken one of those Carters apart, but I've looked inside quite a lot of carbs, so I have some suggestions for you. That needle vavle is held down by gravity. It closes when you let your foot off the gas pedal and the accelerator pump[about an inch away] lets in gas from the bowl. Then when you step on the gas pedal the accelerator pumps gas up that little gallery underneath the needle valve, pushing the needle valve up and squirting gas sideways into the throat of the carberator. If this system is clean and working you get way better acceleration.
On your idling issue, your idle circuit is plugged. Don't always expect that soaking your carb in cleaner for a while will clean out the idle galleries. After you've soaked it make sure you find the little gallery that starts in the bottom of the fuel bowl and goes in past the inner end of the adjuster screw and into the throat of the carb right near the throttle plate, probably below it. If you're blowing air in through where the adjuster screw was, find the two other openings that air can come out; in the bowl and in the throat. Plug each one of them off separately and watch to see air coming out the other one.
I'm not sure what you mean by loading up real bad. ....It almost sounds like the distributor could be a little retarded.
Good luck