At the very least on startup until you say "never show this window again" have it ask you if you want to do tutorial missions. The list OP has there is decent. Have it walk you through the controls as you're doing stuff. The way DCS does its tutorials would be a pretty good template to follow. Fortunately this is a lot simpler than DCS.
Possibly have some kind of hints system in online play too until they check the box to turn it off. If the guy spawns and sits on the runway for more than 15 seconds, "Press E (or whatever key they've mapped) to start engine." If their gear's still down after 15 seconds in the air, "Press G to raise gear." Apply that kind of logic as much as possible. First time their stall warning goes off "Getting too slow will cause your aircraft to stall. Press (whatever button it is by default) to deploy flaps." First high speed dive "Going too fast will cause your controls to stiffen. Press K to trim up." First compression "Going way too fast can cause you to lose control." First control surface lost due to speed "Going way way too fast can damage your aircraft."
It's not enough to have the info available in optional training missions etc, you need to grab them by the back of the neck and rub their faces in the information.
"Move the stick to avoid gunfire." "Stop HOing people, it's mean." "Don't drop bombs on GVs. They don't like it." Ok, those ones might be a bridge too far...
Wiley.
