I thnk what I really meant to ask was HOW many times I should bounce these things back? I mean, the kid has some GREAT profs who are interested in mentoring hu.... should those profs (all writing LORs BTW) not be better suited to the task of assisting their students with grad school apps than two parents (who are still quite stupid - gad_child is not yet 30)?
One of the ways I can tell if a student is going to do well in a grad program is how few times I have to "bounce" a paper back. In other words, after we meet and I give suggestions for revisions and we discuss the essay, it is my expectation that the student will not only revise according to those suggestions, but also think deeply about additional revisions on their own and do them if they make sense. A student who does the bare minimum in corrections and comes back to you for more direction is a problem. All of the advice you've given so far sounds great, why not then just leave it knowing it's now up to your adult child to take what you've given and do the best hu can with it?
Let me agree with those who have suggested that the most accurate advice will come from the student's professors. If they haven't already, they would be more than likely happy to offer suggestions (especially if they are already going to the trouble of writing letters).