As a different sort of contractor the main issue I see (aside for any work promised not done, like the particle board) is that they did not explicitly tell you "When we take off the old roof we'll have to assess the damage. Typically repairs run $1000 - $15k but if we have to fully replace joists this can go as high as X".

What I've seen happen with burnt out contractors is they forget to do this part because 'they've seen it all before'. Yeah buddy, you have seen it all before and the client certainly has not. I suggest asking potential contractors questions that they will find redundant to gauge how they'll handle this kind of information in the future (Information you are likely not to categorically know about). When they say "We'll need to set up a scaffold" you say "Will the scaffold be tied to the building and will there be damage from that?" Just anything you can imagine for each step of the process; The process which you'll have to ask them to outline (Even normal contractors don't really do that unless asked typically).

The fact they had you over a barrel is a happy coincidence for them (I say 'happy' because it's their lack of understanding of how this adversely affects the client that is often a contributing factor (stupid or malicious or both, take your pick)); A comfortable position of investment (by you) that was hugely exacerbated by a lack of information and communication. There are always thoughtful contractors who will go out of their way to describe their process but unfortunately these are few compared to the kind you got.