t-rae

I'm sorry you're feeling stuck! 
My husband got here in Jan 2016, we got married in Feb, and applied for EAD, 131, and AOS immediately. Everything was approved in June, but we didn't get biometrics appt letter until August. The appt was for September, and we received EAD in end of October. 
 
We only JUST got a letter for our AOS interview, to be at the end of March. So it's been a year from applying to interview. Talk about stuck! 
 
However, based on your timeline, it seems to be going faster than ours, so hang in there! Texas is a lot more congested, so your wait shouldn't be too bad from here. 
 
Keep calling USCIS to check in. we called probably twice a month. 

I am sure there is a way to get this resolved. No need to panic and drop everything.
Can you fiancé contact the Belgian police records where he lived (or some type of court office in Belgium) and inquire about obtaining some document proof his record his clean or that I is not available since he was not registered? It may take a little work on you part to overcome this but it's doable.
Have you made a post in the Belgium forum to see what advice you can get?
Put your heads together and cone up with something. Don't pack your backs just yet. This journey is full of bumps and twists in the road. Stay calm and you'll find a solution.