To my knowlege, the NSA does not monitor domestic communications, the FBI does and they need a warrant. In most countries the security officials don’t even need a warrant to monitor domestic communications.
I suspect that the surveillance target was the Israeli agent, not the Congress member. When a Congress member directly contacts the agent of a foreign government, especially one who has been identified as a “risk”, I don’t particularly care if intelligence agencies listen in.
Neither is true. The NSA and FBI have cooperating roles, not mutually exclusive roles. See the Jabarra set of cases. http://www.freerepublic.com/focus/f-news/1550960/posts?page=221#221 (scroll up and down in that thread)
I'd wait to see if anything develops. Other stories name the "agent" as Haim Sabim, a media billionaire (Power Rangers, Fox Kids Network, now ABC and large Democrat donor. I sincerely hope the Bush administration wasn't attempting to wiretap conversations between Democrat donors. Yes he's pro-Israel, which doesn't make him an Israeli agent any more than the NRA is a potential terrorist group.