That should be supported, then; that is the way that Cisco is recommending we design our new DC.

It is as you say. If you dual-home your FEXs using VPC then you cannot use VPC to connect your server to two dual-homed FEXs. A supported solution would be to single-home your FEXs - each FEX connected via port channel to one 7k - and then dual-home ...

You just connect stack port 1 on the first switch to stack port 2 on the second and vice versa for both power and stackwise. The stackwise cables end up looking crossed over each other.

You could use a route-map to policy route some traffic to a specific next-hop IP address or interface.