No clue, never done the FEPH as a vendor. See if the info doc or application gives further info.
Since you got it in before the deadline, you should get a place. If all the spots were already full, they should have posted something in these forums, and/or sent an immediate "sorry, no room" response to your application.
If for some reason it doesn't go, there are still badges available, so you probably won't be sitting outside holding your game. You could also try a very late event submission, and hope they squeeze it in.
Just to be safe, you might want to get your 4 day badges now, since they are close to selling out, then if you do get into the FEPH, I think they will be upgraded to GM badges, and you'll get reimbursed. Now, I'm not sure that is the case, hopefully someone else here can verify that.
Of course, the above only applies if you are not attending just to demo at the FEPH, but would attend either way.