Dallas is a problem office both for USCIS, the Immigration court, etc. They just like to be difficult in Dallas. They're investigating more so it appears that Houston for instance and also coming to couples homes to check on their cohabitation. If you do not hear anything in another 90 days I would hire an AILA attorney to follow up on your case using AILA liaison or the special status inquiry procedures through email for attorneys and try to find out what the problem is with your case. Sometimes its a "name check" issue where your background check is pending with the FBI, etc but who knows. Good luck.
I agree with my colleague
Samuel Ouya Maina, Esq. 415.391.6612 firstname.lastname@example.org Law Offices of S. Ouya Maina, PC 332 Pine Street, Suite 707 San Francisco, CA 94104