Squirt some oil in there to get some lubrication for the air screw. You might have to let it sit over night for full penetration. You are not the first to mush out that screw
I did mine too and ending up having to buy a screw extractor to get it out (Yes, more tool
) What happened was the brass shavings from the screw head work their way into the thread thus make it harder and harder to back the screw out
. Take your time on this extracting saga or you ruin the carb for good. Happy wrenching