Being a middle aged, married family man with kids, I can assure you that never in my years have I seen a marriage start off as badly as yours end up good. This is your life. Accept your mistake, and move on.
Your girl sounds crazy so I wouldn't detail all your plans. You want to protect yourself legally. If the cops show up at the house and she beats herself up, nobody will believe the 280 lbs bodybuilder. You think she is bad now? Wait until you are about to leave. Women are capable of great evil. Move your money into untraceable cash, week by week.
When you are ready for the big move, advise your landlady you are moving out but keep things quiet from the wife. Take her out for the weekend. Have your friends move all your stuff to your new place, and her stuff into storage. On the way home, drop her off at her parents and tell her you are going to the store. Quietly drop off the storage locker keys in her purse. Leave, and never come back. Call her on her cell and tell her the storage locker where all her stuff is being stored (make sure video is taken of the items by your friends). Then never talk to her again.
If you can, get a new job and move away. She sounds like the crazy stalker type. My friend Paul had a crazy sister. She was a total bitch. Psycho really. She managed to sucker a cop into marrying her. The marriage lasted 9 months. She came home on day and all the locks were changed.
1. get fat. stop going to gym for 2 months.
2. start to suck in bed.
3. fart all the time
4. stop buying groceries or doing sweet things
5. watch college football nonstop
6. mutter names like 'bruce' and 'hector' in bed under your breath then deny it
If she doesnt just leave you for being gross
7. Start shitting yourself at random intervals and act like its no biggie. Joke about getting married while cleaning your pants in her presence.
Seriously, the ONLY way to shake a crazy girl is make her leave you. Reject her, and keeping you will become the biggest challenge/goal of her life.