As others have said, an overburdened, COVID-disrupted, and not very competent bureaucracy seems the most likely explanation, and you probably just need to be patient. That being said, there are high profile examples of major snafus in such a situation (google University of Toronto Valentina Azarova for an ongoing one right now) and lower-profile examples of surprise budget cuts and unexpected hiring freezes. So you can't count your chickens before they hatch.
I'd normally suggest giving your contact 48 hours to answer your most recent followup, though due to essentially everything shutting down at end of this week, you might need to accelerate that a bit. Then try to have a phone or Zoom chat with them, not to pressure them (they're doubtless trying!) but to understand the situation. Has the authorized decisionmaker informally said yes, just not signed the letter yet? Has the budget and terms of the offer been syndicated? Be upfront that you're trying to understand how much stock you can place in the verbal offer made. If you clearly make the conversation about "what can you tell me to reassure me" rather than "I'm going to yell at you for not having been successful yet in sorting this out", you'll get a better read of the situation. Ask open ended questions rather than closed, investigative ones, and try to have a chat, not an email exchange. You want to understand the situation, not have your contact fire off yet another email internally and continue to tell you nothing.
Finally, while you do want to let other institutions know you're off the market, and doubtless you and your family want to celebrate and start planning your move over the holidays, you do need to proceed cautiously and not burn any bridges yet. You are very close to having a confirmed position at your first choice institution, but you need to proceed as if that is not yet 100% confirmed. Even though it seems extremely likely it will be.