Wow! The battle for women's rights played right out on your doorstep. Two families, with some similar dynamics. One woman stands up for herself, divorces, calls the police and files for protection. The other woman submissively takes the abuse, lets her husband control the family, right down to who they talk to.
Women's rights sure have come a long way via the law. However this stuff is still played out daily.
You are an excellent role model for everyone involved here. Your kids see you standing up for yourself and not tolerating abuse. You can use this example with words such as how to stop bullies. With your kids coming into that age where bullying will be affecting them, even if only through watching it at school, this is an early lesson. This might be the angle you want to approach this from. I would also several times drill it into your kids heads that they are not the reason for this happening, and that the kids next door have no say in this either, and that they are just obeying their parents.
Now the family next door. You are an absolute threat to this neighbor's modus operandi. Abuse is his style, controlling, and treating his family like chattle. Right now he has them all right where he wants them, submissive to his will. I'd avoid him, but I'd make sure to keep my chin up and never look at the ground when he's within eyesight. I'd stare him down if he looked my way, but refuse to speak. You must continue to send the message to him that you are not ashamed of what you have done, nor regret it.
You are a role model for his wife. Should she ever decide to stick up for herself, she will remember you, the woman next door who did what she doesn't have the courage to do. Her kids, the same. They are not stupid kids, and they know already that their home is abusive.
I would smile sadly at the wife or the kids should their eyes meet mine. I wouldn't speak. But I would send the clear message to the kids--that you are not a mean lady. A simple smile does that. Kids are perceptive. They know who is angry, mean, and abusive--their dad. They know who is gentle and kind--their neighbor next door with the gentle smile for them.
The wife too will know the meaning in your sad smile. She may turn her back to you for a long time, because that is the only way she can justify to herself taking the abuse she does. But she will remember that smile, and you never know what day in which year she will come calling for support. It could take her a decade, or she could show up crying next week at your door.
You are a role model for what has transpired and how to handle it. Be proud of that.