1. Madara already had his sharingan, but simply didn't show it until the clash. (he had been wanting to show Hashirama his sharingan, but he couldn't since it'd reveal who he was.)Hashirama didn't have the power to kill Madara back then. When they were kids Hashirama was slightly stronger until Madara finally awakened his sharingan.
2. Even at VOTE Hashirama didn't decide to kill Madara, until the very last Moment, where he said Hashirama didn't matter or something along those lines. Hashirama has always had the power to kill Madara, however him not doing it is what makes him strong. At Naruto and Sasuke's VOTE battle, Naruto possessed the power to kill Sasuke.. however, him not doing it is what made him surpass Hashirama, who ended up killing Madara.
3. Strong by little? lol alright, thats why Madara deemed it that they'd lose the battle simply because of the fact that Hashirama was stronger than him. Implying that Hashirama was strong enough to decide the fate of the battle.. despite you claiming he was only little bit weaker than Hashirama.
4. The level different between Hashirama and Madara was shown at VOTE.. When you need a tailed beast to help you take on somebody and stand a chance..and still lose.. kind of pretty much shows how inferior you are in front of that person without the tailed beast.