1. i try and keep them fairly short.. often too short and i need another burst or 2 to finish the job... the closer in the less you need to send if they hit tight. i can get an avg of 5-6 kills a sortie with 10-12%... i'm no marksman by any means. i take a fair amount of low percentage shots that seem to work for me... over time your ability to predict what the other plane is going to do will help you get those shots.
2. never really paid much attention and course course many variables such as distance, speed, angle... based on what i think is your situation... it really depends on amount of g's being pulled and it's really by "feel" you shoot as much as i do you're bound to acquire some little extra feel.
3. in combat both planes are manuvering even the slightest motion can throw your aim off. even in a dead 6 chase, both are stressed and making little adjustments. i've never been able to totally eliminate all nose wobble for a dead accurate and "stick to it" placement.
4. again this is experience in the deflection shots. i used to fly a pony and would pull lead.. but you can't do that with the short la7 clip. after a time in the pony i wouldn't waste as much ammo pulling thru to the lead. a good way to give ur gunnery a boost woul dbe to fly something with a decent clip... like a pony... turn tracers off.. and for about 1-2 weeks do that, then go back to tarcers on and you'll see a noticable improvement in both hit% and "feel" for deflection. then go back to the la7...
some of what you've remarked upon is due to simple net lag.. over all it averages itself out.
i use a single dot as well, but one size larger... never really pay attn to them much beyond seeing hit sprites or misses... no idea at what range they register in view while in combat...
an airplane is a fairly instable gun platform.. be happy we don't have to deal with recoil effects, jams, wind, ... etc etc and the fact that the ballistics modeling is assuredly not perfect... but all in all it works out where people have enough success to keep playing.
the biggest difference in my gunnery (not flying style) was upgrading my pc from a 333 p2 where i'd get maybe an avg of 15-30 fps depending and had 7% gunnery or so... to a nice new p4 2.66 and damn fine vid card getting a steady 65-85 fps... gunnery jumped up to 11-12%. and in an la7 that makes a difference.
it boils down to time at the stick... i still flub shots and get amazing lucky ones...
i'll sort thru some films i guess and find a few to post at furballcentral.com with a variety of gunnery situations.