If you guys want the Legion to boost you up a bit and take you seriously, the easiest way to do that would be honesty instead of building up a false story. So far we've had little luck when it comes to lying about stuff. I don't think we have a high enough Speechcraft skill to pull off full on lies. Maybe we can edit the truth a little bit though.
Tell them you're stuck here from another time and place, that you have no idea who sent you here or why, whether it be the works of Akatosh (if you only mention one possibility, let it be this one) another Divine, the Daedra, the Psyjic Order, or any number of factions that may have to power to flip space, time, and reality the bird. However where you're from, the history of Tamriel is studied in intimate detail by scholars across the world. That will get a few looks, but remember, we've had audience with Vivec. A simple letter to the Ordinators or maybe Vivec himself asking if Mike did indeed speak directly to Vivec in person should be able to clear that up. That is, if your Cellphone and Rainbow Dash tee aren't convincing enough. I'm pretty sure the shirt is made of material unknown to Tamriel.
While they might think you're crazy, their outing, if it turns out to be an Ascended Sleeper (I trust nothing 100% in this thread!) then you get some points. And it also somewhat explains your lack of actual magical talent but skill in the advanced mathematics of it. Once you give them a few good nuggets of information and prove your knowledge from the future is somewhat useful, then perhaps you'll be put in contact with the Blades.