I thought that the Dr. was this close to injecting the shapeshifter with some sort of toxin when she pulled his card. When the Fringe crew started to roll up on the lab, it seemed that he had plenty of time to switch the syringe with the process inhibitor when the shapeshifter was distracted. Or did I miss something?
I wondered about that, too. He did seem to have the opportunity to sneak a toxin into the syringe.
And yep...gotta be Walternate, but I'm not sure why he hasn't deactivated the shapeshifters if his world wasn't destroyed. I know that his Peter didn't not survive the crossing, but wasn't the devastation on his side halted when Peter winked out of existence? What would be his motivation to continue his vendetta to this degree? Meglomania?
We haven't really seen enough of Earth-2 (or Walternate) this season to know what's going on over there.