So lets say the Reps gain control of the house and the senate. Does DT then have executive powers to, for example remove the two-term limit allowing him to stand in perpetuity? Or would he need something like the Supreme Court to make such a sweeping change?

Here in the UK we have the House of Lords as our upper chamber. Its unelected and not perfect. Many peers occupy hereditary seats. For example the 9th Duke of Wellington sits as a Lord, direct descendent from the original Napoleonic one! Many seats are clergy. But because it remains unelected it is not exposed to the whims of media like the House of Commons and many attempts at harmful legislation have been thwarted by them over the years.