Advice wanted for child neglect issue

I am out of options and turning to forums to seek advice for an issue I have been dealing with for almost a year. Im not sure if Im posting in the right forum but here goes...

My nextdoor neighbor has a young child who is not yet 2 and there have been some scary situations that I dont know what to do about.
My neighbors moved back into their house last year and from the day they moved in their child screamed non stop aside from a nap break and a half hour walk, once in the morning before people started work and once in the evening after people finished work.
During the rest of the day the child was left pretty much on his own where he would express extreme intense distress with ear piercing screams that went on for hours until his voice was raw and hoarse. We would listen in and the mother would not say a word to him, sometimes for entire days when they were inside the house. He was left unattended numerous times on the balcony where he would climb onto things and almost get over the edge. I heard him fall afew times and his mother would stomp down the stairs, pick him back up, but leave him out there screaming while she went back to whatever she was doing. She also left him unattended in their garage which is just afew steps away from a road which made me anxious aswell.

After a month of hearing his screaming and her neglect, I lost it at her, told her she needed to take him to a doctor and comfort him. Harsh words were exchanged, but she completely denied the problem, choosing to attack me and my family with ridiculous accusations and slanderous lies. We live in a resort style complex and she then proceeded to knock on every single door, telling the residents that I was bullying her into taking care of her child and I was swearing at him to shut up, which I never did and never would. Some of the people that she spoke to had known us for over 10 years and were quite scared by her. So I decided to just let her be and hopefully one of the other neighbors could step in, as everyone had heard the child's screams for help and unhappiness for hours on a daily basis.

I was hoping that this would give her a bit of a wake up call and attend to her childs needs, but instead she started stalking my child (who is a teenager), hanging around our house late at night when her child was left alone inside the house and spying on my child and her friends. She attacked my husband, telling him that she would put our names and address on Facebook in hope that others would come and attack us and threatened to have us evicted, not knowing that we own the house.
Her husband works away for around 5 weeks on and 5 weeks off and I was hoping that once he returned this odd behaviour would stop. It didnt. She did make an effort to speak to her child when others were around, and her husband seemed to have a decent reputation among our neighbors but she must have told him the same thing she told everyone else in the building, and he too started harrassing my daughter, jumping out at her and yelling in her face, and running towards her with his arms punching about when she was walking home from work. After spying on my child while she was at the pool and scaring her while she was walking back to our house, I went and knocked on their door, telling them to stay away from my child, to not speak to her, try to intimidate her and not to go near her and the husband's response was "It doesnt matter, she will be pregnant in 6 months anyway", which I found offensive and untrue and yet another one of their diversion tactics. I did tell the manager, who found it difficult to believe as he had always gotten on with the husband. We also went to the police who suggested a restraining order but then I had advice from others that a restraining order may make them even more angry and harm us or our child.
We discussed this in the privacy of our own home, which they listened in on and went to their lawyer, telling him that we were bullying them into taking care of their child and we received a strange letter from that lawyer asking us to stop doing so. I did contact my own lawyer who brushed it off as nothing and told me to ignore it.

The husband finally went back to his job and we were extremely relieved as our child could walk out of the house without being scared or anxious. However, the wife/mother started up her scary behaviour once again. She would make an effort to speak to the child when others were watching, but when alone he was left inside the house for the majority of the day so unhappy, screaming and crying and being ignored. He wakes up nunerous times during the night which also wakes my whole family up and the mother does not cope very well but in the last few days it has gotten frightening.
She would wake up early in the morning, take the child downstairs, then come back upstairs because our bedroom is right through the wall. She would storm around, slamming doors, banging drawers, smashing the walls and her terrified child would be screaming until he was choking, he was so upset by her vengance and frightening actions. I am guilty of 'paying her back' afew nights ago, I made some noise in hope that she would see how it felt and stop and put that raging energy into playing with her child instead.

This morning and this afternoon got out of hand. She was furious, making a huge noise, I suspect to try and annoy us while her child screamed so hard, he was so scared of her and she just didnt seem to care. I called child services this morning and they said they would make a record of it but not intervene unless he was at harm. I dont believe she hurts him, but she is emotionally scarring him with this anger and I am now concerned about his safety and also the safety of my own family.
I have made recordings of her rages and her poor child's terrified crying just incase child services does finally step in.
The child is so unhappy. I know from other neighbors that he doesnt eat, I know myself that he doesnt sleep, he doesnt talk, he is so understimulated and neglected.
I know also that the mother is not from this country, doesnt seem to have any support or visitors. I have never seen or heard the child have a playdate and the only time she plays with him is when others are around.
Advice on how to deal with this please?