1. His eye did not retain it's light but rather gained a new light after awakening the Rinnegan.
2. Having Hashirama's cells shortens the decade time period, but does not remove it completely as in the case of Danzo.
3. The Eternal Mangekyou Sharingan only removes the damage done by Mangekyou techniques, not Izanagi as shown by Madara who got his eye sealed.
4. Madara did not have Izanagi casted for multiple hours. He set it to activate after a certain amount of time. Do you think Sasuke was using Amaterasu for hours after Itachi gave it to him?
5. Nowhere is it said that having Hagoromo's chakra allows Creation of All Things. The only person who's ever used it is he himself.