The countermeasures don't reduce the chance of hit manyfold, certainly less than twice. Jamming is useless against heat-seeking heads, and flares help only so much.
It's pretty certain stingers can be, and probably were used to attack NATO aircraft, successfully or not. Stinger specimen were found as late as in early 2000s in Chechnya, showing there's still quite a few in circulation.
AN/ALQ-144A and AN/ALQ-157M is an IR jammer, and effective against IR MANPADS. The newest Stingers are IR + UV to defeat this. This is the "disco ball".
I don't know how effective these are (I suspect the primary defense is route planning and flying low/fast), and no one who actually knows the effectiveness would be able to comment.
It's pretty certain stingers can be, and probably were used to attack NATO aircraft, successfully or not. Stinger specimen were found as late as in early 2000s in Chechnya, showing there's still quite a few in circulation.