Alright, here are some things I gathered from watching your films:
1. First video - you are basically in a trap trying to fight about 5 guys at once right at their base. If you are in this situation in a slow turner like a brew, you aren't going to last long. You have to be more patient when multiple cons are around and you don't have friendly support. Fly out and get some alt and come back in. I couldn't tell if you were using flaps, but in that situation or turning fights, you need to use more flaps and throttle to really get around on planes more quickly. In that situation, you have to try for all of the shots you can get quickly to try to down planes as they overshoot.
2. Second video - You need to use more throttle work when coming behind someone. No reason you should have overshot that F4U. You aren't being aggressive enough to slow down and get the shots. Being in a slow spit1, you aren't really gonna be focusing too much on your E state anyway, so just hurry up and kill him. All of your shots are late, in the 3rd video as well. What you should do, and what I do is, put a forward button on your views to "look forward" then press that button, hit 'page up" and then hit F10. This will allow you to look over the nose better and can really help with leading shots while you are shooting. Page down brings your head lower. Some planes you can look really far over the nose, others like the 109, not so much, but it still helps. Focus on keeping your lead in the shot rather than actually seeing the plane. Most players are not skilled enough to get you to lead and then nose down the other way for you to lose them. Normally they continue in the turn, so lead far and trust your bullets and just shoot. Pretty soon you will get a better idea of where to lead with different planes and bullets. Try to set up your shots as crossing shots rather than lead shots. This is the easiest way to hit something.
3. Third video - Your SA failed you. You turned right in-front of that Typhie!! Never turn on a plane if there is another plane behind him. You need to be looking around a lot more. There were times when I felt a plane could hop your 6 and you wouldn't even know, just like the typhie did. As with your first video It didn't seem like you were keeping track of the planes well enough. Look around a lot more and try to keep track of all of the planes around you. Never think you are safe not to look, especially in a turn and burn plane, especially when you are engaging another fighter.