How Did This Ever Happen????

I had a wonderful family and wife that I thought I would grow old with. But, life just threw me a curve ball I’m afraid I won’t be able to handle.
I found out a year and a half ago that the women and mother of my children was cheating on me and our life together ended over night.
Too make a long story short, I have always believed there was some type of mental health issue, but I never thought I’d be in the place I am right now.
I left the home and my 4 kids, Boy's 11 and 9 and my twin girls 6 with their mom and we divorced with no complications. It wasn’t a mess and I did everything I could to just be fair. I was miserable the days I wasn’t with my kids and hated everything about not being a family any longer. I took the kids every opportunity I could and tried to keep their lives as "normal" as possible.
But things started going downhill fast and this is why I believe there is some major mental health issues that I will never understand.
I started seeing that the home was in shambles, bills not being paid and the kids were not being cared for. I would go shopping and fill the house with food. I would take them to the store and buy them cloths and wondered what the ex was doing with the $2000 in child support I was giving every month.
I found out through a mutual friend that my ex was involved in some pretty questionable behaviors.
I might have left out that the guy she met through her work at home part time job was in the military and after a short 3 month affair, he was deployed to Iraq.
During his 9 month deployment, he had her meeting men through a swinger’s website he had been a member of for years and having her video tape her sexual encounters and sending them to him for his enjoyment.
She started drinking allot and it seemed like the person I was married to and knew for 17 years was gone. She wasn’t being a mom anymore and was lost in this new world of hers.
After only a year, her life was out of control and she agreed to let me move back in and let her go figure her life out.
This January I moved in and took over. She moved into a friend’s house and I thought things would start getting better.
After only a month, the guy returned from deployment and my ex disappeared to Virginia for 40 days to be with him.
I filed for emergency custody and was awarded it due to her actions.
She is now moving from Chicago to Tennessee in a week to live with this guy and does not understand my anger about what she is doing to our children.
She sees the kids every other weekend and has not paid one dime in support. She took all her belongings from the home, plus my son’s computer desk and the family room big screen TV. Her reasoning is that I gave her everything during the divorce and that she had the right to take everything in the house if she wanted.
She will tell the judge and her family that she wants her kids and loves them, but everything she does means just the opposite.
How can a mom leave her children voluntarily? How can she think this won’t hurt our kids?
I am trying everything I can do to keep the children safe and protected from this person we no longer know.
I am up at 5:15 every day. take the kids to school by 7am ( camp now that it summer), go to work as an engineer with a pretty stressful job, run to pick them up by 6pm. home for dinner, homework, baths, a little family time and to bed.
I fear I’m going to get burned out and all I want is to give my children everything they deserve in life.
She has selfishly left not just me, but her children, and family. She shows no emotions and truly believes this is the right thing to do.
The family and I believe she is Bi-polar or BPD. Her mother died when she was 12. Her dad became a drug addict and was also in and out of mental institutions until his death a couple years ago. Her childhood was hell in my eyes.
I came from a boring but stable childhood in the suburbs of Chicago. My parents are still married after 40+ years. My sister is a layer and my brother is a doctor. And even knowing about her childhood, and emotional issues, I loved her with all of me. I thought I could provide her with everything she wanted and give her the security she so greatly needed.
I care about her well being and don’t want anything bad to happen to her. The kids need both of us, but I no longer can make excuses for her behavior. All I can tell the kids is that mommy loves you.
I don’t know what to do and just hope that I can be strong enough to keep it all together.
If only people around me day to day knew any of this.
I’m a single dad surviving only on the strength of my kid’s hugs and smiles.