Iran already knows his bluff. Abbas Aragchi even explicitly mentioned this in an interview, stating that negotiating with the US is a pointless exercise, but it tells the Iranians whether Dump is planning a major strike. So there's definitely going to be a major strike happening by Friday or Saturday.

To end the war, Iran will demand a full withdrawal of US forces from all neighboring countries as well as a shut down of US bases. This will also have the added benefit of giving them full control of the strait when the US leaves, and a free hand to bombard Israel. The GCC are already fatigued from a war they had no say in, so if the Iranians strike the desal plants, they will either join the US offensive or they'll kick the American troops out.