Rich,
A lot of good advice given to you. Bench/steady rest, back off on the powder, check your fired patches, and practice dry fire.
The only suggestion I can offer is, if you dry fire, do so with your gun unloaded. A loaded but unprimed flintlock can still fire and rather consistently, too!
My loaded flintllock rifle gunnes can fire UNPRIMED 3 out 5 times.
With open sights, I was taught, rear sight, front sight, target, FRONT SIGHT! When one stays focused on the front sight, that fire coming out the side ain't near as bad. You'll get used to it.
Working up the right load for your gunne is a lot of fun. Getting good with it is fun too! Each one is a different character (just like those old Italian motorcycles I used to ride). Have fun!
Regards,
Johnny