Oh this sounds like a major headache.🤦♀️ I'm so sorry you are dealing with paperwork errors like this. From the sounds of the roadblocks you are hitting though my only suggestion might be that If SSA cancelled "the other 2 pending SSN applications' maybe your husband could start from scratch again and begin the process of applying for a new SSN seeing he has his Green Card in hand. Make an appointment with local SS office, take the GC and all your documentation and start again. Maybe the "mismatch in immigration status" will be removed once the 2 pending applications have been cancelled. Good Luck👍 !!!