After several emails back and forth Avis have offered:
After a careful review we will honor your base rate of $320.85 and process a refund of $887.45 from your charged base rate of $1208.30.
Assuming they actually pay up I consider this a win, though I can help but feel they should have offered some goodwill also considering the additional expense (2 extra Uber trips to secure a car), not to mention added stress and hours spent.