Your first two things....we're not the only country in the Iran deal...second, he's backtracked on bailing from the Paris climate agreement. His stances on various important issues change daily so who knows what he'll do. His head is surely spinning as he figures out what he can/should do and what can he get by with.
I don't care about other countries involved in the Iran deal. Iran has already violated the deal with no repercussions. Iran has spent billions on arms from Russia. Iran now has billions that we gave them and are expanding their support for terrorism throughout the region.
My guess is that Trump is going to wait until Iran further violates the agreement. Then he is going to tell our allies, the sanctions are back on again. They can choose to trade with Iran or the U.S., their choice. They can choose to stay in the deal with Iran or oppose the U.S. and risk other reprisals, militarily or otherwise. We carry a very, very big stick.
The Paris Climate deal is dead, Imo. Trump is going to exploit all of our natural resources. The EPA is going to be turned on its head as many regulations will be overturned. Keystone approved. Dakota pipeline moved forward. Federal lands opened to exploration. Many, many jobs created. Mines will be reopened. Clean coal technologies will receive lots of federal funding research.
Amnesty overturned. Not sure about DACA. Trump will change it to deport felons, but not sure what other changes to expect.
For insight, look at his appointments for Energy, DOJ, EPA, Etc. All very much like minded with respect to my comments above.