USA visa - what to do if my plans have changed and I don't pay visa fee

[otp]

I've been trying to apply for the USA visa as a Home Ofice Refugee Travel Documents holder. A week ago I have completed the online form on US embassy website but I have not paid the visa fees yet because the dates for the interview that I was offered are so far ahead (Jan-Feb) and I was hoping to be able to travel to the USA sooner in December. So now my plans are kind of ruined. I know I cannot travel to the USA in February or later because I will be busy. Another thing is I have applied to be a British citizen so by the time I will finally get my appointment I might already have a British Passport and I will be able to apply for a visa waiver then. And generally my curcumstances that I have listed in the application will have changed (such as for example my main document used for application will no longer be TD but British Passport). So I'm thinking there is no point paying quite an expensive $160 + visa fee because with visa waiver you only need to pay $20 or something. What should I do now? What will happen to my already filled and submitted online application if I leave the visa fees unpaid now? What if I decide to abandon this application and can I just start a new one when I get British passport? What if I pay now and have time to travel only when I already have received my British passport but my visa would have been stamped on my TD? Am I legally allowed to travel using Travel Document when I already have British Passport in posession? Also in case I get the passport the Home Office will probably ask me to return my TD so I need advice.