I am not with Laminar Research; just a flight simmer.
Firstly to run X-Plane the DVD version disc 1 has to be inserted at all times. There is no activation key with the disc version. The key supplied with the boxed version is a sales gimmick to lure you into buying other stuff from the store.
I have the same problem of not being able to use a USB dongle as was made available for version 10. I was advised to try and make an ISO USB substitute for Disc 1. At this stage I haven't tried.
To achieve what you want, try downloading the digital download demo version from Laminar Research. The demo version is the full version but has a time sequence and a fixed location until you provide an activation/password key supplied when the official purchase takes place.
When you start the program and disc 1 is not inserted you will get an automatic request to provide the activation key or insert disc 1. In your situation try the ISO USB dongle instead. Will it work this way? I don't know. You can only try.
Good luck. I will send you a personal message to ascertain how you created the ISO USB dongle