if he didnt have kyuub, hake would have killed him. or, if haku was being merciful like he/she was to sasuke, orochimaru would have killed him in the forest of death.
Kakashi said Naruto himself had 4x the amount not Naruto with some of the Kyuubi's chakra.
Yes, Naruto can still go Sage Mode and fuse with Ma and Pa toad which lets him stay in SM. Naruto can beat many strong ninjas still like the 4h Raikage (Naruto shadow clone went SM and used his sensory ability to sense the 3rd Raikage's attack and countered him). So Naruto can avade A's attacks with his sensory ability then counter with frog kata ( even if A blocks he'll still get hit by Naruto's which killed 1 of Pain's body so it will hit A since it's direct hit) or use Ma and Pa genjutsu to stop A then use his giant rasengan or rasen shuriken on him. Sasuke will lose by getting hit with frog song and a rasen shuriken. Beat Tsunade (she can't heal from the rasen shuriken). Plus he can focus on training to learn more wind jutsus and a 2nd element.
if you take a major event out of his life (being made a jinchuriki) that means he would've still had his parents alive, that means he would've got taught by minato himself when he was a kid and that by using his enormous chakra reserves (he's an uzumaki after all) without kyuubi's interference (don't you remember that in part 1 jiraiya helped naruto use his chakra properly without kurama interfering and not letting him use jutsus properly) he could've got even stronger. Minato was also friends with jiraiya so that means that jiraiya could've taught sage mode to Naruto earlier in his life, even though he wasn't a jinchuriki, Jiraiya was always looking for the "child of prophecy" and training the child of prophecy from his book (tale of a gutsy ninja, main char is called naruto) would've been very fitting. He could've got as strong as he is now or even stronger, who knows...
