All the advice given has been terrific, so I only feel the need to add my two cents because your situation is all too familiar - projects that begin with the architect heralded as the answer to all the client's dreams devolving (and always triggered by a dispute during construction) into the architect seen as
in the way; even pointing out life safety issues somehow seen as unnecessary meddling.
I've actually had clients, upon hearing a contractor neglected to install hurricane ties in a review of framing I performed with the engineer, bark "haven't you ever made a mistake?!" I was berated for giving the contractor "a hard time"!
My take on your situation is simply try to avoid litigation at all costs. Lawyers and arbitrators only value the exchange of services for fees- in other words, yes you would get what you deserve in terms of money and likely indemnification should you need to walk. But, I assume your work, it's quality, and your reputation, is more valuable. We invest so much time and energy into a design, walking away from one is a terrible loss-even if paid in full.
To that end, I salvaged a client/architect relationship that had turned snippy/distrustful with forcing the client to step outside our contractual interaction just for a moment, and have a meal and drinks together- and just talk like human beings.
They got festering resentments, I wasn't even aware of, off their chest and I was able to explain that I was on their side and the successful completion of their project was as important to me as it was to them. (My standard line is they will quickly forget bumps in the road if it turns out beautifully, but will be reminded daily if the result is a compromise)
I don't know what you relationship is with the client, but as I'm sure you already know, it's hard to get back to mutual respect once the kind of back and forth you describe starts.
But the effort might be worth it as it's a small world.
Best of luck,
Julian King AIA LEED AP
juliankingarchitect.com