Pseudoarthoses are not uncommon with ACDFs- especially with allograft (cadaver graft) and with the older Cloward technique. You do have to make sure that your pain originates from the pseudo (there could be other pain generators).
If your pain is from the pseudo, then you could be a candidate for a repeat ACDF with autograft, consider allograft again or have a posterior fusion which generally causes the front to fuse also. An artificial disc replacement would not work in the face of a non-union.
It might be worth looking outside the VA.