Sorry to hear the bad news regarding both all 3 parties but I think there are a couple of things worth pointing out
1. Steve and I have done a heap of deals (large and small) over the time I have known him. 1 thing stands out about him and that was his effort to rectify any issues no matter how small ( i only ever had 1 small issue and he was always determined to sort it out although I always explained it was okay

). His postage method and effort made in the hobby is second to none and that is from my own experience and I am sure many can share a similar experience. If there is some personal/work/financial reasons for this claim then he is one person who wont be happy until its sorted out
2. A main part of this hobby is the occasional impulsive buyer and I have been caught with this myself, if it wasn't buying a card I really could not afford at the time or even busting one box too many

but in the end, anything that we spend our disposable income on needs to be managed to avoid it taking money from Bills etc
Giving credit to people is never a good thing and I am guilty of doing it from time to time but I keep it at a manageable level $30/$50 and the person would need to post up a deal here regarding the due payment date

Letting someone bust hundreds of dollars of boxes without paying is just irresponsible of sellers and will always leave the door open to not getting paid at all by the irresponsible buyer with a bigger desire to bust than what they can possibly afford.
3. Covering yourself as much as you can should be a no brainer and doing Deal threads on OCT are there for a reason ! Not putting all information in that section is something I don't understand. If something does go wrong it will be easier for others to help if they really know what the deal but I can also understand keeping it a bit private but surely a deal of this magnitude would warrant all fine print put into the deal ?
In the end, I hope it all gets sorted out and that others learn from it in a positive way.