Summit County has two Nordic Centers offering excellent cross-country skiing, as well as a Tubing Hill for kids of all ages.She went on to say that we cannot mention places like Breckenridge and Keystone, because a traveler might think to copy that word from the listing, go to Google, look it up and end up renting an accommodation directly from that place than the VRBO listing.

We're trying to find something that is no more than 15-20 minutes from Kailua, reasonable commute to HNL, and land that will accommodate a great view.

Is it legitimate to write off the cost of the travel and accommodation as business expenses to see how others do their vacation rentals?

Most people generally will be accommodating as long as you are taking initiative and being mindful of their obligations. 

An overview can be found here.The CMHC web-site also has a mortgage calculator which will accommodate high-ratio, insured mortgages.My recommendation is to learn the underlaying principals, be able to perform the calculations manually and develop your own spreadsheet.  

AirBNB specifically recommends language pertaining to allergies and service animals - you can state in your listing that you don't accept any animals (don't say "pets") due to allergies and it being a health risk to you or a family member.Again, definitely look into the laws yourself, but between this being your primary residence, your only STR, and you having allergies, I don't believe you could be required to accommodate service animals.

For one thing, Reagan National Airport (DCA) is very small, limited in the size of aircraft it accommodates, and already really busy.

I'd definitely add a refrigerator and some appliances to that floor: toaster and microwave to make it more accommodating.

I again tried to be accommodating to my tenants, since it was their move-out day, so I had it 2:30-5:30 pm.

That's an interesting perspective; local to me I haven't really seen that, but I have seen a lot of buyer's agents insist that they host the appraisal, which we happily accommodate and I prefer.