He also has no real idea of how govt operates and no interest in finding out. I doubt he understands basic eighth grade civics about the operation of each branch and what's in the Constitution. -- He knew what judges should be on his shortlist. He has more than an idea. He also has help in Pence to deal with Congress.
He also has no core principles or beliefs. To the extent he has any minimal ones, they tend toward the left. -- See the judges he listed. Also understand that centrist views are historically American views and he will be effective at making progress on a host of issues because of his centrism. I am actually glad to see you figured out he's a centrist.
In and of itself that's not disqualifying. He is impulsive and lacks mature judgment. He is also petty and vindictive to the nth degree. He is not good at details or organization. He's not a great businessman. He is a great real estate idea guy and developer. There is a big difference between those two. He is also a great self promoter and reality TV guy. None of these skills equal a chief executive of the most powerful nation on earth. The things you mention about him are simply visible symptoms and evidence of this. -- Personality issues mostly, can't argue with you there. Not a big enough reason to not vote for him.
Finally, he will demagogue up any issue simply to get elected. He no more believes this immigration crap than I do. Historically, he's been a moderate on the subject who took Romney to task over it in 2012. The fact he will say anything to get elected is very disturbing when coupled with the above. -- He's already working with Mexico. We need a border and we need to deport people who come here and commit crimes. Those are his minimum planks, and it's a good start.
In short, he's unqualified.