Beat the game about 30 minutes faster on my second time through, so learned alot. Got the bad ending once again, so decided to do some isolated save/load state practice on the final section. If you miss your shots or die you have to start the game from the beginning and get the bad ending. You only get the credits for getting the good ending, so now I dont consider my bad ending playthrough a legit beaten game. I think the game doesnt loop when you get the good ending too, so its intended you get the good ending to beat the game.
After about 20 minutes of isolated practice on that part, I have a good idea of what to do. There will still be luck involved but I have a good chance. I should break through eventually.
For the final part you have 4 or 5 shots only and can take 3 hits from the boss missles. If you touch the boss sheild its insant death and replaying the game over, which would take me around 30-40 minutes again. I found getting up very close to the sheild and firing immediately, regardless of sheild positioning, and being in middle of the boss, gave me the best chance of landing that kill shot. Once I break through I will put up a tutorial with commentary and maybe edit some parts down.