Electronic spark control problems

[86-C10-V6]

Sounds like you may have multiple problems.
You need to examine the weights and springs that perform the mechanical advance. The easiest thing to do is to remove the distributor and replace the weights(lubricate well) and springs and the vacuum advance.
If you want maximum flexibility, use one of the crane adjustable vacuum advances, but just replacing the old one with a new one may fix part of your problem.
You can buy weight kits with springs relatively cheap.

The ESC generally does not advance the timing, it only retards it.
This is accomplished with the tip in vacuum switch and the spark knock sensor on the engine block.

If you are getting to much advance, it is not from the ESC doing too much, it is from the ESC not working correctly and bypassing it will not fix your issues.

The ESC should not impacting your timing at idle.
Once you get your mechanical and vacuum advance fixed, you should be able to check the ESC operation by using your timing light and tapping on the exhaust manifold with a light ball pen hammer. This emulates spark knock and you should be able to observe the timing retard when you do this.
Hope this helps.