The negotiation is complexed with too much thinking and too little serious process. Here I am not talking about the Iranian side, Iran has actually played very honest and good game. I am talking about the American side.
It is quite simple. Iran has argued for and aims at a setup where they retain their ability to produce energy out of uranium, by itself. This includes the ability to enrich uranium to a certain degree. The ability to enrich the uranium above five percent is not needed in a peaceful industry.
So it is basically about the ability to enrich uranium. This ability, including all the machinery that makes uranium above five percent, should be abandoned, and all the rest should be retained.
In this way Persia wins the ability to produce peaceful energy out of uranium, and the rest of the world wins the peace that follows a Middle East that does not run amok in an arms race.
So the American negotiators should focus on the ability to enrich uranium, and the processes that follows in a production aimed at nuclear armament.
G-d bless the peace.