Why are there so toxic people?

A few months ago I started to get along quite well with a woman of about 38 years old, it should be noted that I am 20. I think that to a certain extent you can say that we are family, she is something like a fairly distant aunt. She is quite sociable, friendly and so on. Her husband, he is younger, she is about 28 to 30 years old, he is quite known for having children with different women (he is the toxic one) he works for the government in security, therefore he is away from home for quite a while.

Well, what I'm saying is that I started to get along well with the lady, we started to have more communication for different reasons and well, so to speak, we became good friends, sometimes she asked me to go to her house to check her internet connection (I half understand her on that subject) and well, I stayed a little longer to talk, she has a son who is about 10 years old, he was always present when I went and never left us alone. After a while the boy had more trust in me and even received me in a good way the few times I went.

Obviously I had communication with the woman by message, she had given me her number and from time to time we sent messages, one of those when her husband came on vacation, I think she took his phone and cloned his WhatsApp. Since I was used to sending her messages, I sent her a Facebook post where I said something like "What would you do if your friend started dancing like that with your son (a photo appeared of a lady dancing but quite attached to a boy), well I sent that message and I also added "haha, that's my situation", obviously I wasn't referring to the lady, I'll put them in context very quickly, in a family gathering, you know drinks, music, dancing, which was a few years ago. I was sitting and suddenly a lady who is a friend of my mom's arrives and asks me to dance, I have never liked to dance so I don't know how to dance, and well I told my mom's friend that, but she told me that it didn't matter and as soon as the music ended and the husband arrived, he was already drunk, he arrives, grabs his wife and asks her "what about him?" My mom comes over and her friend tells her that nothing is wrong, she calms her husband down by telling her that "he's a child, he's not going to do anything" and that's it. Well, I was about to tell that story to the lady you talked about, but I couldn't because she told me that she won't send messages because she thought someone else was seeing them.

Until then everything was normal, then we continued talking normally, I never thought that the husband was so toxic or jealous, but so much so that he got to the point of contacting me on Facebook obviously with a fake account, but obviously I already imagined who it was, he told me several things all based on jealousy and things that who knows where he got it from, after that I stopped going to the lady's house to avoid problems for me and her. From time to time we would just talk by message but I was already moving further away from her.

After a while, the woman's husband sent me messages again through a fake Facebook account and I already told the woman and she told me that she would block him (I felt that she already knew that it was her husband who was sending messages, because I don't even doubt what I told her) so I listened to her and blocked him.

After another time when I didn't even talk to the woman anymore, the husband sent me a message again something like "and why don't you talk to your love anymore?", to avoid problems I didn't answer and blocked him again But he was not happy, recently he tried to contact my relatives, my father, my brothers. And I don't know what to do anymore, obviously we prevented him from having contact with my family but we don't know if he is going to stop harassing us or if he is going to continue trying to contact us.

What do you think I should do?