The sanctions were working? News to me. The Iranians I've known all painted them as painful for the common people, but not the sort of thing that led to general unrest, as they knew it was as much to blame on their leaders as it was on the United States. Basically we're punishing the citizens and getting no net political traction on the ground, because they're as frustrated with us as they are with their own government.
The nuclear end of things was handled well enough in the deal. The quality of uranium they are being provided with is virtually worthless for weapons manufacture on any reasonable timescale, particularly with the low number of centrifuges the deal allows. Furthermore, their most robust nuclear facility is going to be put in a state where it would take years to get it back to the sort of facility where enrichment could occur. Our inspectors have the right to inspect any facility they are suspicious of, and if Iran tries to hide things, the deal is off. Their nuclear program isn't completely dismantled, but it is, at the least, frozen. The real problem is the expiration of the ballistic missile embargo in 8 years- that would allow their program to rapidly accelerate if not renewed, and will allow them to be nuclear-ready within a couple years of the program being discontinued.
What really concerns me is the massive cash influx with little to no oversight in regard to Iran's funding of terrorism. We should have given the money back in graded fashion over the course of the deal, with future transactions dependent upon Iran ceasing all funding of terrorist organizations and activities. One slip up, and the cash stays frozen.
As to suitcase nukes and the like- for such devices, plutonium is required. Iran doesn't really have the capacity at current, and certainly will not be able to construct a facility for creating such devices under the current deal. They could in the future, but this deal limits them to 200 kg of nuclear material. To make even a rudimentary portable nuclear device would require roughly
11-15 kg of pure plutonium, which would take damn near forever with such a small stockpile of starting uranium and such a low number of centrifuges. Even making a Little Boy-style WW II nuclear device would require 64 kgs of pure uranium, an amount they could hardly spare for a test given their minimal allotted stockpile already.
