Car dropped 250 RPM and is now stuttering

Check the voltage at the MSD running. There are a few places where you can get some voltage drop and you just want to be sure it is near to the voltage level at the battery.

Unless the FBO plate moved, then it would not 'just show up now'. Please re-check the timing advance with the vacuum advance hose pulled and plugged. Your 50 degrees advance at 2200 is a problem but the vacuum advance is in the way of getting the right data.

You need a solid baseline of info for cranking compression, vacuum at idle, and timing advance at various RPM's for future work and troubleshooting.