To add...
Asylum is not an option due to the safe third country agreement.
this is really important to consider, and take in consideration here.
Please do not go to the border and ask for asylum. He can not do that and will be deported if he does so. last thing you want from what I can see.
He would need to ask asylum in the US, as he arrived there first. If he does go to the border, they will send him back to the US border, and then he will defenetly get deported....
My husband was illegal in the USA. We are still waiting, 19 months later for his Visa He never was deported or asked to leave at any moment. He left out of his own free will. I can t tell you yet if it impacted his application or not, but it has made it that much more longer. Our lawyer told us that by the law he is not inadmissible, BUT it does reflect poorly on his character.
On the opposite hand we had really strong submission for proofs of our relationship, and I hope that this will weight in positively.
Also consider that if you indeed decided to get married and go through with the application it is most probable that he will have to go to Pakistan anyway, if he is called for an interview, as he will have to apply at the embassy from his home country...
I know that people who have entered a country legally and have overstayed their VISA, in some case, can apply within that country, but you would have to look up what the conditions are, as I do not recall them exactly right now.
I tough my case was hell, but I guess could be worst...
Good luck