@Marilyn64
Hi - your place looks amazing - reminds me of many happy days spent in Georgetown.
You are describing a common problem - how to get to the top of the listings for a city or area. And, there is no way to really engineer this as you are competing with thousands of other hosts in the DC area.
One of the things that will push your listing a bit further down the listing on a general search for the DC area is your limited availability. In addition, as you probably know, new hosts get a bump up, liistings with a lot of activity and Instant Booking also get an uplift, Superhosts as well.
In addition your are in the upper price bracket (and rightly so). Would you consider a base price for say, 4 people and then an extr £xx per person per night for anyone over that. It would make your property appeal to medium size groups as well.
All you can really do is edit your listing on a regular basis - just changing some text, adding a new picture, etc will have some impact - although limited.
Finally - if I was coming back to your area, I would set the filter straight away for Georgetown!
Good luck