70 302 starts, but won't idle :(

I've got a 1970 coupe with a 302, Edelbrock 1405 carb, Edelbrock performer intake, hooker headers and stock points/condenser system.

I bought it running a few months ago, but it wasn't running great. It ran rich and at a high idle. It would die when I first put it in gear, unless I took off quickly and drove it around for about 10 minutes, then it would be fine. It also had less power than expected.

I replaced:
-Distributor Cap
-Rotor
-Spark plug wires
-Spark plugs (with copper plugs all gapped to .035)
-fuel filter
-Vacuum lines running from the vacuum advance to the carb, and lines running off the intake manifold

After that, it ran slightly better but still not great. I tried to adjust the carb, but the idle mixture screws did nothing to the idle and if I lowered the idle below ~3K RPM, it would die.

Next, I rebuilt the carb. I changed all the settings back to stock including the idle and idle mixture screws which are now at 1 3/4 turns out.

Today's the big day of the first startup after the rebuild and the engine won't run for long. It starts right up if I hold my foot into the pedal. The engine runs at 3000 RPM and sounds smooth if I rev it higher. As soon as I try to let off the gas, the engine will die. No idle at all.

There's also a new noise. Before it dies, at around 2000 RPM, there is a whining noise. Its not a squeak like a belt makes, but a whine that goes with the engine speed. It will be higher and quieter at higher RPMs, but louder and slightly lower pitched at lower RPMs.

Any ideas?

What method would you suggest to find the vacuum leaks?

I've heard that I can disconnect one line at a time and cap it off, then start the car and see how it runs. But then I thought running the car without vacuum advance might damage the engine or cause other problems..