So if Lorkhan's Heart was found Shor could be revived some how?
Where is the Heart?
If Tsun died and is in Sovngarde, why is Shor not there?
Shor was there. You were Shor, or more specifically, Shor's Ghost, a Shezarrine.
"Seeing the strength of King Wulfharth, Orkey summoned the ghost of Alduin Time-Eater again. Nearly every Nord was eaten down to six years old. Boy Wulfharth pleaded to Shor, the dead Chieftain of the Gods, to help his people. Shor's own ghost then fought the Time-Eater on the spirit plane, as he did at the beginning of time, and he won, and Orkey's folk, the Orcs, were ruined." — http://www.uesp.net/wiki/Lore:Five_Songs_of_King_Wulfharth
Y'see the parallel?
What if the elves took the heart to some plane of Oblivion? How'd that effect everything.
Why would Wulfharth need to plead to Shor to fight Alduin if he, as a Shezzarine, could have himself?
He was Shor's Ghost. It's pretty clear within the text. Otherwise Shor was openly walking around Tamriel, something we have never seen another example of.
Why would they word it in a way that makes it sound like Wulfharth and Shor are separate then? Wulfharth pleads to Shor then he later watches the battle of Shor against Alduin in the spirit plane and learns a shout from it. It doesn't sound like it is saying the two are the same in that passage.
Well the Greybeard's have been known to sing Shor's Ghost into the world.. (which lay all powers low)