Before the nuclear deal was signed in 2015, Iran was almost beating the economic sanctions that were imposed on them. Had Iran stayed on course, its resistance economy - which was adopted at that time - would've developed much deeper, and their nuclear project would've gone much further than it is now. So while nuclear deal brought some benefits, including releasing the $150 billion USD that were freezed earlier, and delivery of S300 PMU2 air defense system, it looks like it was a setback for Iran in the long run.
IMO, moving forward, Iran would be better off by pursuing the resistance economy that they've started earlier, move their economy from its dependency on oil, and have a control of the group that called themselves "reformists" camp - who seem to naively believe that the EU would always comes to their rescue.
Lastly, Iran shouldn't negotiate on its missile development. If they do, they would be committing a suicide.
Where there's a will, there's a way.