I mentioned elsewhere that if Trump is short, it’s only going to be by about 100 or so. He’ll easily be able to get 100 Cruz delegates on a second ballot if/when it becomes clear that the GOPe is going to pull some BS move.
There will likely be at least 200 or so uncommitted delegates, not including delegates who will have been released by candidates who have dropped out. Contrary to popular belief on FR, they will not all be RNC drones. If Trump really is very close, uncommitteds will put him over the top.
Ryan and the Establishment are just scamming foolish big donors.