If you file for adjustment of status one of the things you need to prove is whether you were inspected and admitted to the U.S. I-94 proves that for you. The USCIS might know the place, manner and time of your entry. Make no mistake the burden of proof is on you. They will ask you to provide your passport and I-94 when you go to the adjustment of status interview. I encourage you to request a replacement of your I-94 even for future references.
Even if your get married, immigrant visa is not immediately available to your wife for you are not a U.S. citizen. Make sure your wife stays in lawful immigration status until visa becomes available to her. If you are eligible to become a U.S citizen, do it as soon as you can.
Well, more facts are needed to answer your question. The insurance refused to pay for what? property damage? Medical? ... If it is about property damage, it depends on; what type of coverage your friend has, the circumstances surrounding how you borrow the car, whether you have a valid driver license etc. You better consult a lawyer in person.
If your labor certification is approved, some of the work is done. Since these matters are sensitive I urge you sit down with an attorney to review your documents. Tee fee depends on which attorney you go to to. Attorney might charge you for two hours of work.
Hard to say what kind of a win, if any, he is entitled to with the limited fact you provided. What state did the assault occur, how bad was it? what was he charged for? All these and other facts have to be reviewed. I suggest you call free legal aid in your area.