Holley Idle mixture screws non responsive?

Get the initial up to the 18-22 range and try again.

If the engine shuts down with the screws all the way in, they are working.

What is the idle drop from out to in gear? It may be bleeding mechanical advance in and when it drops into gear,that advance is gone, compounding your issue. Is the initial timing at idle the same in neutral and in gear?

If you can't get to the secondary adjuster, use a feeler gauge and open it about .004-.005, that should be about 1 turn of the adjuster if it's 24 pitch. Definitely check were the plates are in relation to the transfer slots.