How can you say there is no shame to put a healthy young horse to sleep when there are obviously other options, there are people who will take on a rig, there are charities etc I don't think PTS should be talked about so lightly! Especially when this pony obviously is well behaved and good in...
Have you requested previous owner take the pony back with no refund? If charity or PTS is on the cards surely that would be a better option. If he is as good as you say he deserves a chance by someone and not to be put to sleep.