Frankly, I don't think you'd really want the template. You've already soaked all the LA you can afford, so getting more templates means losing actual class levels, and Unseelie Fey doesn't offer anything to a Wizard. Even Chill of Winter could be more harm than help, since it forces you to close to melee range.
As for the Auras of Despair...I don't know. If it was actually two separate characters, I'd say definitely...it's a untyped penalty from different sources, so it should stack. But Dvati are really really weird - according to their Dragon Magazine writeup, you 'treat them as one character sharing two bodies'. It's DM final ruling, but I'd consider it to overlap instead of stack, the same way a Large creature doesn't take -4 if its body occupies two separate squares covered by the aura...it's still only one Aura of Dispair, it just has two simultaneous emanation points.