1. I get the difference between REFIT and READY for drawing replacements; I am still confused why, for example, my Romanian Armor Div. on REFIT sitting right on the RR will not fill-out its TOE of light tanks. Am I missing something?
Two issues that come to mind are supply lines and production.
If your unit needs 100 tanks and you have 100 tanks ready for deployment, the unit might still not get all 100 tanks in a single turn if its supply situation is bad. Or rather, the amount of replacements you get is not directly based on supply, but since it's also measured based on the distance from the HQ and the railhead, bad supply usually means bad replacement rate.
Production is rather simple, if you have a single unit set on refit that needs 100 tanks, and everyone is on lower-priority ready, and it's sitting in good supply, you might still not get 100 tanks if you don't produce 100 tanks or don't have enough tanks in your pool.
5. AIR WAR still mystifies me; I know to keep the airbases close to the front to minimize flying distances, but what results do you get from pulling various levers in the settings? Confusing.
Percent Required to Fly - this basically says "How many planes do I need to be available before I'm allowed to fly a mission?"
If you set it to 50%, then any air unit that has less than half of its planes combat-ready will not fly any missions at all.
If you set this higher than 100%, this will pretty much prevent any missions from happening at all. Setting this to a low value such as 5% will cause your air units to fly more often, but it may also cause higher casualties in terms of "more planes to shoot down" and "operational/wear-and-tear losses from flying so many sorties on the same plane"
Air Mission Setting - this basically says "If I'm allowed to fly a mission based on the previous setting, how many planes should I send on the mission?"
For example, if your Bomb Airbase setting is set to 60%, then whenever your order an air unit to bomb an airfield, that unit will send 60% of its combat-ready planes to bomb the target.
If you set it to a high percentage, you'll obviously send more planes, although this may cause more casualties from enemy fire and operational losses, possibly to the point where the air unit's strength goes below your Percent Required to Fly
Air Mission Escort Setting - this is the same as the Air Mission Setting, except for fighters. That is, if you set Bomb Airbase Escort to 60%, then any fighter unit that gets selected to provide escort to an airbase bombing mission will send 60% of its available fighters.
Keep in mind that making the percentages for the escort and actual air mission equal will not guarantee the ratio of the escorts to the bombers/transports. If you have 100 bombers available and 50 fighters available, your Bomb Airbase Escorts percentage would have to be double your Bomb Airbase percentage in order to maintain a 1:1 ratio of bombers to escorts, such as 50% of the bombers and 100% of the fighters to get 50 planes of each type.