I say if we kill the deal, Iran holds more cards than we do. They could just go back to developing their nuclear program as new sanctions wouldn't necessarily work any better than they are now working with North Korea.
Meanwhile I think we can acknowledge that the current president of Iran is, I think, trying to reform things in Iran a bit. He should get some credit as he is in a precarious situation.
From this article it says: The international body overseeing the deal, the International Atomic Energy Agency, has said Iran remains in compliance, as have Secretary of Defense James Mattis, Secretary of State Rex Tillerson and Joint Chiefs of Staff Chairman Gen. Joseph Dunford.
Administration officials in favor of keeping the deal in place have been looking for a way to split the difference between saving the deal and saving face related to Trump's campaign rhetoric.