Holley 1920 issues

You pretty much have it on the brakes and on the rear wheel cylinder adjustments. See where that gets you. And, you may just not have a well bled system.

BTW, the gauge you got with the carb may be for dry float setting, which is done when the bowl a float are off. My recommendation is for the wet float setting as described; that scale may or may not work for the wet float setting. It may not cure you issues, but is an important baseline setting for any carb.