Relationship breakdown

In January this year my, then, wife started being extra distant and strange with me. She was locking herself in the bedroom and talking to people on VRChat, she was being secretive about who she was speaking to, always hiding her phone conversations and texts, etc. By February I was beginning to get suspicious as I'd not slept in our bed for over a month and basically wasn't allowed to. She didn't want to get close or do anything but deal with her "friends" problems.

In March just after my sons birthday I caught her having immersive cybersex with a random guy, as it turns out she had started an online relationship with multiple men from across the world. When I walked in on her she told me to get out of the room and close the door and carried on doing it as if there was nothing wrong. It completely turned my world upside down after 15 years. We have 6 children and were living a modest lifestyle as a result. So paycheck to paycheck, always putting the children 1st. 

A bit of time went by and I decided I shouldn't have to keep putting up with it so we spoke/argued about it and one of us had to move out, this was decided to be me, although I was the one paying all the bills and I still largely am paying for the mortgage. 

I have no friends in the area that they live anymore because she went around telling people that I was an abusive and controlling husband and she left me because of that so I couldn't move close by because everybody thinks that is true. In reality, I've been led to believe that she said these things to rationalise what she was doing to make herself feel less guilty about the way she carried on.

I had to leave my home, my children, move to rented accommodation in a place I don't even know to be as near to my children, while still being near my own support network. I'm paying a fortune in child maintenance and I do get to see the children whenever I want but I feel like ultimately I'm the one being punished for her selfishness.

Not only all of the above but her parents know what she has done and yet treat me like I'm the one who ruined it all. I dedicate most of my free time from work to go and see the children and they all make out like I'm a deadbeat dad that does nothing for them. I can barely afford to feed myself with all my money tied up in paying my rent, bills, child support and travel to see the children so I'm not able to either treat the children to a nice day out or treat myself to anything, yet, my ex has had 3 holidays without the children, several men around the house I'm paying for and even introduced the children to some of them. Whenever I seem to have any time to myself she'll come up with a reason for me to be there and if I can't make it tell me I'm "letting the children down". There's no way I'm able to live my own life and I have to stand by and watch her live her new life with her multiple partners. Her parents know what she's doing wrong but seem to ignore it entirely to make their own lives easier and have even validated what she's doing to her on numerous occasions.

I have no idea what I'm asking here but does anyone have any advice on how I can live my own life, deal with having no money left every month because its all tied up all the time and show everyone that I'm a good father and not the false picture they're painting of me?