What could possibly go wrong?

Oh, a lot could go wrong, of course. None of this is great. But given the choice between just "up and leave" without some sort of agreement, and sitting down and hammering out an agreement, the latter is almost certainly more in our interests.

It's easy to identify a possible off-ramp for both parties. That deal is one where Iran gets substantially the same or better terms as they had under the JCPOA and/or were willing to agree to before this war, but it has one or more "extra" subjects that weren't covered under any of those things that Trump can claim as a win (even if they're not that important). For example, you could just repeat the JCPOA terms but add a provision that says Iran won't develop an ICBM. That last bit would be no skin of Iran's nose, but it would let Trump and his supporters claim that unlike that terrible Obama, this deal covers missiles, so thank goodness for President Trump!

The real obstacle is that Iran has notoriously been difficult to negotiate with. They have historically strung out discussions, failed to empower their delegates to make any decisions, change terms in midstream, and favor very lengthy and cumbersome processes. And that was before we pulled out of the laboriously negotiated JCPOA and attacked them during prior diplomatic processes - there's far less trust in the process today.

We don't know for sure, but most of what we know of Trump points to him not wanting to still be negotiating this deal in 18 months. He likely wants a very fast path to a deal - which is not really Iran's thing. He is at least acting like Iran is under serious time pressure with the embargo. Hopefully that's true, but if it's not it may be difficult for the U.S. to hold the line for a strong deal. High prices are going to segue into actual shortages for a lot of economies in the next few weeks, and that's going to make things more difficult for the U.S. going forward.