It is not an optimistic scenario you present.
Once a crime is labeled an “aggravated felony,” there is limited relief that is available to a petitioner. Because AFs cover so many crimes, an individualized analysis of your case will have to be done by an experienced immigration attorney.
Your I-797 is simply to notify you of the status of your application or petition. Once you receive your actual green card, it can be used to apply for your Social Security Card and a state issued driver’s license. It can also be used to prove employment eligibility in the u.s.
I agree with Attorney Tanijo. File for divorce, if you choose. Skip the I751 interview, if you are so inclined. Or, you can go to the interview and express your concerns. The decision as to whether she gets a PGC is with USCIS. In any case, be aware if your motivations.