How did Madara start the Infinite Tsukuyomi without the Divine Tree? What was the thing about the third eye and him sucking up the tree?  I thought he already had the Ten-Tails inside of him.
Madara doesn't need the Divine tree for activating Infinite Tsukuyomi.
The only requirements to activate the Infinite Tsukuyomi are the ten tails chakra and the Rinnegan.
The divine tree is just a Jutsu that complements this.

For more information about the 2 Jutsus: 

http://naruto.wikia.com/wiki/Infinite_Tsukuyomi

http://naruto.wikia.com/wiki/God:_Nativity_of_a_World_of_Trees