so if it means returning some of their cash, so be it...as for Iran cheating on the JCPOA, check out the linked VOX article that deals with that very question...
Getting IAEA personnel on Iranian soil is our best shot at avoiding military action and or total Middle East chaos that spreads to the whole world...as someone else said..."Perfection is the Enemy of Progress" (Churchill?).
All that being said, as you suggest, we need to continue to find ways of blunting Iran's support for terrorism...let's hope that inroads can be made with the sizable 'Moderate' population within Iran and help them gain influence.
Link: https://www.vox.com/2015/7/14/8963503/iran-nuclear-deal-violation