All of the above seems to be true, but does not answer your questions, that is, who to talk to in TSA to get an official answer in writing. Sorry, I can not answer that directlly. However if you will go to the TSA web site I believe you will find a way to submit the question or get contact information that may or may not work for you from the land of OZ. If you want to persue this and can not get the answer you need, I will be willing to research and make calls for you, but I am slow and my wife says unreliable. If you do want to apply for clearance, even though it is not requilred, you wil need to do that after you arrive in the states, I think, as you need to present yourself and be fingerprinted, etc. all of which gets expensive and time consumming.
My professional oppinion would be to not get the clearance for two reasons. First because FAR and TSA regulations do not require it, and second, because you are not enrolling in a flight training program. You all ready know how to fly and there is no FAR 103 training authorization.
However, US flight training does require that individuals take and pass a yearly training course on TSA proceedures and safety. This is an online course that takes about an hour to complete and a certificate of completion is available. I would suggest that you bring that certificate with you in order to flog any overzealous TSA officials. In reality if you can make it through the airport security check for the flight over, you should be good to go. Welcome to the good old USA land of the free and home of the brave. Would you like to trade houses for a while?