If the base timing advance was set at 1500, then 10 degrees is not enough. If the vacuum advance is in, with throttle open too much, as you try to set idle speed down, timing will be way too retarded. If you know how to set static time try 15 degrees or a few more, otherwise try 20 to 25 degrees at 1500 RPM, then reset as idle and mixture are tuned.
Also check the throttle plates, primary and secondary, see if they are able to close properly. The primary needs to be per post #8, to insure idle circuit functions.
