...until I learn OOP better. Then I can master PhpFox or Elgg.
IMHO this *is* the answer to your "can you think of any limitations" question
My question is, do you know or can you think of any limitations that I should consider before putting any more time into my ADDT application?
the main limitation to worry about is, that ADDT currently isn´t compatible with PHP 5.3. Other than this it´s clear that applications built with ADDT only provide comparatively basic "web 2.0" (aka AJAX) features except for a handful of components such as the form controls -- AJAX features which are supposed to provide additional functionality will have to be added manually, and it´s up to you (and your application´s "audience") to decide if you can live with this limitation or if your application should provide all those AJAX bells & whistles which would be hard to integrate into ADDT applications.
I know(through reading quite a bit on security) that I’ll need to simplify my url’s with http rewrites, to keep mean people from hacking my url ID querie...
Well, if I wanted, I could also change a "pretty URL" to something completely absurd and see if you - the developer - did provide a "oops, this page is not available" custom HTTP 404 error page
However, in case your ADDT driven application does what you want it do do, and in case a 3rd party application such as PhpFox is too hard to learn, you might still consider sticking with what you´ve built so far. In my opinion the real value of any web application is the degree of control which you, the developer, is able to exercise -- and in case you do know your ADDT driven application inside out while struggling with getting 3rd party scripts to work for you, I personally think the case is clear.