What should I do about my marine wife..?

Well to make it a long story short, while my wife was deployed in the marines, I cheated on her with her best friend and impregnated her too( I have been dating her friend for three years now, I have been married to my wife for four, we married at 18 so i could get her benefits from the military). Now I really have no way to support this child and the woman said she was going to keep it. I have never had a job because my wife had been supporting me but recently when she came back from her tour she caught her best friend and me in bed. She launched herself at her and in attempt to defend the love of my life I had to hit her to protect my girlfriend. We are all young, we are all 22 so really my wife still has time to find another person. One day though I came back from a date with her friend and she attempted suicide. I was against her enlistment in the marines, I never really have supported war like she has. I think her suicide may have something to do with that fact the she may have killed some and now feels guilty for the horrible thing that she has done. I really do feel sorry for what she has done but frankly I just really wish I can move on with my life and marry her friend. She is a burden on me and my girlfriend. Is there any place where I can dump her off, it needs to be cheap because she does not make a lot of money and she only has 12,000 dollars in the bank. Which I am taking 11,000 of to help pay for a down payment on a house that I am buying with her friend to start our family. What can I do to make this easier on my girlfriend she seems to be under a lot of stress because of my selfish wife, she just won't stop bothering her all. At night we can hear her crying all yelling and my girlfriend is PREGNANT. She needs rest but my wife is acting like a baby. Please help