In my opinion Sandman, what you have written seems to be an indication that this is "a" right school, if not 'the' right school. With 50% in merit it answers the financial question. Having his major, assuming the school has a good reputation with that major, answers the education question. Only your guy can answer the social question, probably after his overnight visit. Top 10 ranking with recent appearance at CWS and supportive of your son? Answers the baseball question.
I'm convinced that once you answer these there is not a lot more you can do to get assurance of being on the roster. From what I've seen, many of these schools carry as many as 40 players on their 'roster' (some have JV teams as well!) and a representation by the coach that your guy has what it takes to get on that roster is about the best you're going to get.
As to making the 25 man travel roster that's a whole other hill of beans; one that probably should not be answered until the coach sees what he has and who can beat out who. As your guy progresses, he will continue to compete against the new guys. It's as it should be.
So the question of coach integrity is the only other open question. For this I would say that you should be able to track down alumni and competing coaches to help answer that question.