Re: I think Donald would do that to send a message: "Don't do this to us."
I doubt that Trump would do it to send a message. Politicians spend all their time "sending messages" as a substitute for actually achieving anything. Trump is a businessman, not a politician. If Snowden gets sold down the river it will be in exchange for something, as a bargaining chip in some back-room deal. If the US wants Snowden, then Russia will need to get paid. And if the DoD wants Trump to pay Russia, then Trump will need to get paid. So the question becomes, how can the DoD scratch Trump's back.