Edit: Scratch that, the Therian name replaces Sacred Beast /facepalm I dunno why I was thinking of Incarnate, anyways I definitely prefer Sacred Beast.
As for the Kyurem formes BST, no... 720 BST should go to the complete Original Dragon only. However, B/W Kyurem are actually stronger than Reshiram/Zekrom obviously and have so far been presented as such. A 700 BST makes the most sense to me.
Kyurem no energy = 660 20 points under Reshiram/Zekrom
Kyurem fused with Reshiram/Zekrom = 700 20 points over that of the Tao duo.
Should look something like: