stalling with AC on, coming off of idle

I disconnected the wire going to the AC compressor and moved all of the levers to various climate settings. The blower fan came on as expected, but the compressor never came on. The car didn't stall. I plugged in the compressor wire and the compressor kicked in. The car did not stall. I moved the car out of the driveway and shifting from R to D caused a stall.

I checked all of the vacuum lines. I found another cap that was cracked and replaced it. The PCV hose was very loose, so I added hose clamps to either end.

Using my timing light and vacuum gauge (manifold vacuum), I tried to adjust the timing to maximize the vacuum and until the engine sounded the best. I took it for a spin and it stalled in the driveway. I pulled the valve cover and checked the valve lash, adjusting to 0.12 for the exhaust and 0.09 for the intake (recommended by the cam mfr). I pulled the #1 plug and it looked good (grey brown) and the gap was 0.035. I found that the plug wire for #1 was pushed back into the boot pretty far. I readjusted the wire and reinstalled the plug and wire. I started tinkering with the timing again. I adjusted the AFR mixture screw to slightly rich. I can get the idle vacuum up to nearly 18", but kicking on the AC drops it to 14" and then going into R or D drops it even more (following the RPMs). It was getting late and I was hot, so I upped the idle and drove it around the block. No stalling. I'm at the edge of the adjustment slot in the dizzy, so I'll need to loosen the bottom bolt and readjust the slotted plate (I hope there is room for it to adjust). Idle timing at roughly 900-1000 RPM is roughly 20'.

What should I do next? I'd love to get the idle down a bit, since the car wants to lurch pretty hard when I move it into gear. And it still has a very occasional miss. Continue with the ignition timing? Smaller spark plug gaps? Move plugs and wires around? Compression test? Leakdown test? Spray some sort of aerosol and check for vacuum leaks?