The L drivers from SAPP don't recommend using the dive-flaps as such a tool.
1) To answer your first question, it really depends on your altitude. The higher you go, the easier it is to compress. A lot of the information out there likes to milk just how easy it is to get into compression, but it really isn't too bad. When I dive down to attack enemies in the P-38J, I'll usually be rudder-ing side to side, and rolling slowly with closed throttles because chances are that the enemy's going to rip him/herself apart if he/she dives at full throttle.
At altitudes below 20K where I hope you're doing your jabo work, you'll find it hard to get into compression under 470 mph. When you're dive-bombing, you never want to be going full throttle anyway.
2) Most of my approaches towards ground targets are weird. They are from either directly above or, if its some Osti or other, I'll usually circle it while pitching up and down, roll over sharply and rocket it. This prevents it from hitting you as you get closer and closer. It's usually a sort of preference. I never have to even consider using dive-flaps in jabo work.
3) Depending no the target, the alts differ. They can be a max of 5K if I'm trying to avoid ack. That being said, I almost never attack alone. I'd need a wingie to divide up the ack.
4) Operations... not too sure what you mean. Do you mean the order of dive, shoot, attack etc? If so I usually circle the field and then simply fly in from a high angle and shoot at a few targets, then zoom back up, but not perfectly straight up. You have to take all precautions to avoid ground fire. I never fly level over the field for more than 2 seconds either.
5) Using the dive-flaps should only be used if you REALLY are in desperate need to get out of compression. Never have I used them on a BnZ run. Used improperly, they'll just cause unnecessary drag and your zoom wont be as good since you did not have the speed you could of had during the dive.
6) Keep doing what you're doing. When in the P-38J, I use trim to get out of compression with no throttle. When flying 109's, I do the same thing. In the P-38L, you can use the dive flaps but you can always trim out as well. Upward elevator trim and the plane should pull itself out. Like WW said, you're going to have to disable combat trim because as you go faster, the CT will push your nose down in an attempt to stabalize your plane. This is not good since you want to go up, which is why we trim up during compression.
Perhaps the SAPP boys can correct me on some things as they have MUCH more experience than myself, but these are my suggestions and they've worked for me so far.
