Many of those things are indeed areas of concern. I wish he would cease and desist with his Twitter rampages, but he seems to be under the impression that it is somehow doing him good. I also agree that his lack of specifics is problematic but he isn't a person who is used to explaining himself, so I don't know what to tell you. I am somewhat heartened that I'm not an American at this time in history.
Part of me is still caught by the comparison to George W. Bush. He crafted a persona that was that of a slow country bumpkin, the simple, non-too bright "old boy". Many people have reported their shock when they met with him in person and found an informed, cool as a cucumber individual who very much in charge person and asked very good questions.
I tend to think that Trump has to be similar in private and that his public persona is just a well crafted caricature designed to throw people off the real man. Well, to be sure, he has been rather successful in also putting a lot of people off, but hey... To his credit, I have not read a single report of anyone who has come away from a meeting with him saying what a mental midget he was or what an uncouth buffoon he was. Most reports glow about his charm and intelligence. In contrast to his public persona that is just plain weird reading. You would expect people running off to trauma therapy if they met with the buffoon behind closed doors.