318 2bbl won't idle without choke

Been chasing a carb issue on my 69 Barracuda. The car is a 2bbl Carter 318 with the original engine and carb. I've been bringing it back from a long slumber since buying it in April.

I've replaced the entire ignition system (plugs, wires, ballast resistor, distributor with all internals, coil) and have the timing set to 10 BTDC. I've rebuilt the carburetor with new gaskets and a general cleaning.

The car will run and drive pretty well if the choke is at least ~25% of the way closed, albeit with a slightly high idle. Other than feeling like it's a bit more sluggish than it should be, it's not bad. However, even when warmed up all the way it won't idle with the choke open. If I bump the idle speed up a bit, I can get it to very roughly idle, but touching the gas kills it right away.

The mixture screw is set 1.5-2 turns out, but oddly enough adjusting it has no effect on the idle. Several turns in either direction seem to do nothing.

I've done propane torch / carb cleaner / cover the carb throat tests for vacuum leaks and haven't found any yet. Any other places I should look?