Amelia, my 2 cents worth - despite feelings and the loss, which are normal and factual in this case and all our cases being in similar situation; people who are taking the time to advice you 'are not against you' and FWIW, not many can do better [than Gillian, Huma, Helen - they always give best, most correct and measured replies]
You are experiencing normal indignation & the loss is considerable, however one can't forget that we are not dealing with inst. organisations or corporations; with large resources, logistics and layers of customer support; + deep pockets. Amount of money $1.700 is considerable and you being a Nurse [a good guy, a career, and one of most needed person's in society] means the Host won't do much wrong even 'despite stated rules' if they go the extra mile in order to be flexible with you.
Like it was suggested already; being tactful with Holly & Chris and suggesting, IF they can re-book your Dates then refund you - would have been most optimal thing to do [minus airbnb fees which they cant refund you] Best of luck for next time - as this one is double harder, you were not going for holiday but WORK [travelling nurse, as you state in your post]