> I think "Iran was considering a peace deal" is a bit of a stretch here.
Iran was considering a peace deal. I agree that the most plausible was they would reject it.
> What does Iran still have to lose? Well, a lot.
The US could do this, sure, but then Iran would have even less to lose. This might work if the US started small and threatened escalation to try to compel Iran, but the US started at massive escalation so any additional airstrikes are likely to be less escalatory and thus less of a threat.
Even worse, there is a fundamental problem with madman theory, if Iran believes they are dealing with a madman, then threats aren't effective because a mad man doesn't keep promises. If you think your opponent is not rational, then you should not expect them to follow cause and effect.
> Iran is never going to capitulate, until it capitulates. Their rhetoric is going to remain that the US has no more levers and can't change anything, because admitting otherwise invites those levers to be engaged.
I agree that we don't know exactly how much pressure is on Iran. Iran historically has been willing to suffer almost any cost. During the Iran Iraq war then sent enormous numbers of teenagers in human wave attacks over and over. It is my estimation that the current war with the US has helped to stabilize the Iranian government and that they benefit more from the war continuing than from a peace deal.
The only military lever the US has left on the table is an invasion of Iran. Maybe limited to the coastline or maybe complete regime change. Trump has not even attempted to bluff that he is doing this.