Can someone explain the ending? SPOILERS

Who shot down the Uncle?

If the Russians did it, that breaches the exchange and the Americans keep JL.

If the Americans did it, the Russians become really suspicious.

Whoever the snipers were, were they supposed to shoot whoever it was who came out?

Did Nate know that Jeremy Irons wasn't going to be under the hood?

Also, for some reason I thought Nate and JL were supposed to be in London when Nate got tortured. They were actually in Budapest? (I thought after JL got tortured she was going back to London)