First you say the F-5s are bad and now this? Are you doing a bit?
That’s not true, it has nothing to do with your crews repair rank. The game just has a threshold for how many important modules can be critically damaged before it stops you from repairing.
That’s also not true, i once watched an F4C get farmed 3 times trying to take off from a forward Airfield. He died and counted as dead each time he got strafed and ended up with 3-4 Deaths on the Leaderboard in an ARB match.
So you can definitely repair “Dead” planes, as i mentioned above the deciding factor is which modules are black and how many of them are black, not your crew skill or if you count as dead or alive on the Leaderboard.