it sounds like you're chasing a massive vacuum leak, and you're fighting a battle on two fronts with separate janky/unknown carbs.
the one with the borked screw might be a lost cause, the other "NOS" one likely needs a rebuild. or you may find yourself needing to source yet another carb that's known to be in good proper working order.
establish some basics first: like checking the timing, confirming the mark on the balancer corresponds with TDC, making sure the plug wires are all in the correct order, the manifold is tight, you have the right base gasket for the carb, all the hoses are routed to the correct ports or blocked off, you have fuel flow both at idle and at speed, you have free and unrestricted air flow, you have full throttle, the accelerator has a pumpshot, you don't have a loose wire or incorrectly wired components in the ignition system. your float bowl vent isn't blocked off. and so on and so forth.
it's a long and tedious process, but all of these things can add up. it's death by 1000 cuts, a little here, a little there and you have something that's undriveable.
confirm the basics. establish a baseline. then work the tree from there.
