Well thought out, and yes 'unpopular', analysis. I agree with most of your comments.
One question though: "Why is a convention nomination (not brokered) 'not gonna happen'?
I think first that Romney will go into any convention either already the winner in delegates or very, very close. If close, he will make sure to have one of the lesser candidates in his pocket with promises, so that would not be pleasant for us.
On the other hand, watch out what you wish for: if it is a TRULY brokered convention, the most likely winner would be Jeb Bush. I don't think any of us want that.