I think he will do at some of the things. Congress swill block others.The most important thing,as Steelhead mentioned is the appointment of 2-4 new Supreme Court Justices.It a Democrat gets in and he/she gets to appoints those justices, the United States as we know today is doomed, if it is not already from the current POTUS .
In my view, based on what I know about him and from those I know who have interacted with him, he is a good man with all the principles and weaknesses that one might expect from a successful businessman, I have myself known and interacted with more than a few of those, and believe me, I have known much, much worse.
I see him as in it to win.
I take him seriously about wanting to clean up many aspects of government that are totally screwed up and he really does have a talent for surrounding himself with talented advisors. You know the points; he has mentioned them often enough. (Economy, national security, military, tax system, health care, etc., etc. )
Thus I do believe that he could accomplish much that we all want and would try hard to get there. I also think that he would get more results than the others.
You are dead-on that the biggest single issue is cleaning up the Supreme Court. I have personally known and spent time with the two good ones and to a slight degree back in law school with Ruth Ginsberg whom I do not favor. Some scholars and pols may say that Constitutional principles permit flexibility and change to honor developments in mores and values. I know all about that, but in many respects that argument has gone way too far. Trump would strike a good balance in getting candidates who respect the original principles.
Now, he may not succeed. There are other decent ones. If he does, though, I'd love to see Cruz on the Supreme Court to face up against Roberts.