No questions. Just move on. Engaging in public spectacle isn't a good look for anyone.

That's normally good advice, but this is a small enough niche that trust-in-brand matters a great deal. Right now AdaFruit is looking like the villain here. I think a little more transparency from them is a very good thing if they don't want to suffer massive brand damage.

Definitely avoid ad hominems, and focus purely on facts. Provide what information/evidence you can without violating agreements, but only if it's relevant to the situation and includes as much context as possible.

No in this case addressing the accusation is necessary.

I think what's currently been said is sufficient. You need to make a grown up version of the statement "None of that is true", but yes probably best to leave it at that.

Honestly, this being Adafruit, my default assumption is to believe them. Especially with this super vague "please read between the lines because if I actually say something false it'll be libel" accusation.