Helmet looks great !! You've done a really good job thinking about the air flows and your thought process to remedy the downfalls of the helmet. Not very many folks would go to the trouble to analyze this and come up with a solution as you have done. You might want to move your hot air exhaust fan, rolled down toward the back and moved down a little. Depending on the CFM of the fan, it should pull warmed air from that entire side of the helmet when it's being exhausted.
The reason for moving it down is to prevent the airflow from hitting your face or anything else and causing turbulent air movement before leaving the helmet. I believe rolling the discharge angled back slightly will
move the exhausted air away from you and dissipating better. In case you were standing still, it would prevent the discharged air from migrating back toward your helmet. I hope that helps, that's my official HVAC opinion !!