I am confused, does the N400 NOA now provide GC extension?
Regardless, you are in a tough situation, and first and foremost you need to make sure to keep yourself safe along with all your important documents. Your wife cannot withdraw the I751 as this is your petition, and you can change it to a divorce waiver, so make sure you keep all evidence of the abuse along with the police report(s) and court records that you mentioned. If you filed the N400 based on the 3yr rule, withdraw it as you cannot pursue that option with a divorce. If it is based on the 5yr rule, you can still pursue it.
Get yourself a divorce lawyer to deal with the divorce and try and claw your funds back. You can remind your lawyer that your USC spouse, and maybe others if you have a joint sponsor for your CGC signed an I864.
Good Luck!