After seeing all of those messages, I panicked and filed a PayPal claim - and that somehow closed the eBay return. [emoji33] I received an email to that effect from eBay.
Thank you! This is the first time in over 15 years that I've ever tried - or needed - to return a purchase from eBay. I guess I've been lucky up until now. Well, except sabotaging this return by filing with PayPal! I guess that's what I get for panicking and working on this late at night when upset and exhausted.
Now I have formally issued a complaint with American Express and they have been great. (So far, anyway).
I am really sorry you are going through all of this but I think the problem is that you are going after too many sources of resolution. Ebay would have stayed involved but you contacted Paypal. It may be too late but you should have waited for an answer from Paypal before contacting Amex. If it is not too late you may want to put a hold on the Amex complaint. I expect any of them would result in a resolution in your favour but it gets confusing if they are all going after the same thing.
ETA: I can understand why you are panicking. The seller is playing every card in the book and creating all kinds of havoc. A hacked account is for fraudulent buying not fraudulent selling.