Regarding #3, I haven't kept up with this specific issue lately, but wasn't the issue with their use and creation of HEU, atleast for a while, that they wouldn't allow UN nuclear energy inspectors to monitor what was being created at the reactors? There are AP articles from 2023[1] saying that Iran had barred 1/3 of the most experienced inspectors the UN had there from monitoring it, and a news article from the UN itself from this year[2] says that Iran has been actively impeding their ability to monitor its nuclear program.
Presumably if you allow monitors for non-weapons uses, the accounting of where the material goes is relatively straightforward. Therefore monitoring could not be allowed, ipso facto, they are doing it for weapons.
An other compatible explanation is that they wanted ambiguity about their weapon production.
Besides, wasn't this whole thing triggered by a UN report showing they had made a lot more 50% enriched stuff than expected? I.e. the monitoring "worked"
But ambiguity with respect to weapons production has to be taken as a confirmation of an intent to develop weapons of the opposite side. Which makes this equivalent to just having a nuke program. It doesn't even give you a bargaining chip because there is nothing you can do as a step back (since you didn't do anything in the first place)
[1]: https://apnews.com/article/iran-nuclear-un-inspectors-b82c92... [2]: https://news.un.org/en/story/2025/06/1164291