According to Tobi....according to Tobi the Kyuubi attach on Konoha was a natural disaster (Tobi states this to Sasuke in the same conversation that he speaks about Izuna); but later we see the account that Tobi summoned the Kyuubi to Konoha.
He was lying then, and I believe the whole account with Izuna is a lie as well.
Madara and Izuna were twins. It is possible the body we see in the coffin is Madara after his Rinnegan has been removed.
I agree with you again when you say "how the heck can you lose ur eyes to a blind man and while u pssess usch power?" Logically, Izuna voluntarily gave his eyes to Madara in order to obtain power. These two obviously planned everything out together. The two could read the Sacred Uchiha Tablet, they knew the secrets.
Madara could have easly implanted a new sharingan into Izuna. It would make sense that he return power to his younger brother who he cared for. The Sharingan that Kakashi and Tobi have is always activated (supporting that Tobi's Sharingan is also borrowed) but being an Uchiha, Tobi can use the Dimensional Mangekyo to its fullest extent while Kakashi requires preparation and suffers side effects (which supports that Tobi is an Uchiha child).
Naruto 562 Page 2. We see a flashback from when Oonoki is younger. He and Muu are speaking to Madara about Hashirama. If Madara was alive with Oonoki and Oonoki is alive and old now. Izuna could be alive and old as well.
I just think that Tobi is a lying sack of shit! (yes i said it) he lied to Sasuke about some details about the Uchiha past just to make everyone believe he was Madara. He is not powerful enough as just Izuna, no one knows Izuna, but Madara Uchiha-Power in a Name blah blah blah. I am so over this guy and I cant wait till he gets OWNED by someone.