> What prevents the next president, who just might have more than a 1.6% vote margin, from just reversing all of this?
The way things are going the next president will be a simple continuation from the present one. The vote margin will not matter.
> On a different track, if Trump does a large amount of governing by fiat, will Trump accept the blame if things go awry? That seems like the flip side of dictating new rules.
No. It will be someone else's fault.