1. Minato dealt with Kurama after Obito left.
2. The deal Obito made with Itachi already covered why the former didn't attack Konoha again over that time span.
3. You're assuming that if Minato were to attempt assasinating Obito with FTG, Obito was going to be stupid enough to try the same exact thing he did the first time around, or that Obito wouldn't have already learned the dimension hopping ability by then.
4. His gamble paid off. Whether you agree with it or not, the results speak for themselves.
5. Of course Kishimoto had to justify Minato dying on the night Naruto was born, because Naruto was supposed to be the main protagonist of the story, not Minato. That's why the story's name happens to be the same one as the name Minato gave his son.