I had some question about score calculations that I can't find in any of the official material. So I'll ask here in the opes that someone knows. All questions refer to NON-perk points.
1. How is 'kills hit percentage' calculated?
In fighter mode: % of rounds hitting enemy planes.
In attacker mode: % of rounds hitting planes, gvs and objects.
2. what is the scoring formula for pilot kills? For example I know that landed kills score more points than non-landed kills but what exactly are the point values for each? Also, is it a progressive scale? Meaning does landing 4 kills earn twice as many points as landing 2 kills? Or does it earn 4 or 8 times as many points?
"Kill Points" are largely damage points. You get 1 point per kill + points for any damage inflicted on the enemy plane. Thus you would get 1 point for a proxy kill, and you will get a lot more points for killing bombers (they absorb more damage) than fighters.
3. It looks as though Ditching does not count as a death for purposes of the kills to death ratio, I was wondering what constitutes a ditch? If I ditch in enemy territory and I am captured, does that then count as a death?
A ditch is when you get the "ditch" message

It's simply based on the closest
base: If it's an enemy one, you will get captured, if it's a friendly one, you will get a ditch.
And a ditch is no death for K/D purposes, a "captured" is. (CV's are bases too, factories aren't).
For GV's it's a bit different, you can safely "land" even deep in enemy territory as long as no enemy is around.
4. Does shooting a non-airborne plane on the runway scored as a kill and does it count towards the pilot's rank?
No difference between killing planes on the ground or in the air. (Apart from a few more unfriendly comments on CH 200 perhaps)