alternator causing bad idle??

I spose it's possible that the battery is far enough down, and with the alternator not putting out much at low speed.

ONE THING you need to do, is related to the problem that time after time keeps showing up, and that is, voltage drop in the system harness and connectors.

With the car doing the best you can for idle, measure the battery voltage AT the battery, and then at the ballast resistor, or better yet, measure the drop directly

To do that, put one probe right on your battery pos. post, the other on the "dark blue" supplying ignition voltage to the ballast.

With the thing idling very slow and low alternator output, you might just find it's got a lot of drop, there.

You have an AM radio? It sound OK? Another possibility is that one or more diode/ winding is failed in the alternator, and this will not ONLY cause low amperage, but a lot of "hash" (AC ripple) on the 12V system. It is possible that this can interfere with the ignition system.