If you have a big cam the outboards seem to like from 1/4 to 3/4 turn out from fully closed, if a stock cam one full turn will work usually. Make sure the power valve is not opening when idling in gear as far as fixing the broken off tangs on the idle mixture screw you may need to replace the baseplate. I would have heated he base plate up with a hair dryers first to loosen the corosion up between the brass screw and the aluminum You may still be able to do that with a very small EZ out and the proper drill bit Good luck