I'm "Sail Away's" husband so your experience resonates with us. I am not a regular here I post more often on Reddit under bethelrmayflower.
I feel your pain as my wife left me several times because she was so confused and conflicted. I totally get the anger and feelings of betrayal. After all from our point of view they choosing some scam artists over us. You want to kick something or worse. I have no idea what your situation is other than what you wrote.
What I can do is tell you about my thinking and it is up to you to decide if any of this applies to your situation.
When SA (sailaway) left I was angry and hurt and lost and lonely and scared. It seemed like it was over, it sure looked like it was over based on what was said and reasons given etc. I went to a nature walk in town and had a good time. I was flattered that three single women were giving me a lot of attention. Some guys flirt and attract attention and some do not. I'm one of the ones who never wears a wedding ring and have never had a problem, so this was new to me. Apparently, nurses can be very consoling. But then I got to thinking that it's not over until it's over. I still loved SA and even though she said she didn't love me anymore. She is a good person at heart and any pain she caused was not from her but from outside forces, the cult being the biggest.
This happened several times and she never gave up her religion but came back anyway. She didn't have JW family to make it harder like your wife does so there is that difference.
It took a long long time for SA to finally kick the cult and we are still suffering because of it. But it is much better now.
We don't know your new SO but a woman who would take up with a man with a child only four months separated from a spouse is at best making rash decisions.
Look; even in the best of circumstances where two people are as compatible as possible, with no problems caused by family, career, children, jobs, sex, health or money marriage is hard, damn hard.
But the problem is every marriage has at leat one or two of those issues. Then you through in crazy JW crap and whoa.
You said something about the JW's breaking up families. Yes, they do but in this case, you have a choice. In my case, I decided that if my marriage was going to end it would be zero percent on me. I never said one thing angry, I made no legal moves. I made it so that if SA wanted a divorce she would have to make it happen with no help from me.
It could be argued that you are the one breaking up your family by bringing in another person.
It could also be argued that if your new girlfriend is a real loving stand-up person that cares about you and your family the minute she hears about your situation she would insist that you do whatever you have to do to make it work for your wife and child and if it didn't work in two years you should look her up.
But here am I dishing out tough talk and I don't even know you. Notice that I said it could be argued not that it was true.
Please don't be angry with me, I mean no harm. It is obvousely your choice how you live your life and no one can judge you except yourself. It is just a point of view from someone who has 30+ years on you that might be of use to you or not.