I'm not a lawyer but I was in a similar situation many years ago. You could it mark down to experience but I suspect, as with any case or abuse, it has a profound emotional echo on you today.
I personally think that depending on your part of the world you see if you can go down a legal route to hold the company, the culture and the manager accountable. After I left my job I read this book. It helped get everything into a lot of perspective and understand the toxic dynamics playing themselves out.
I personally, wouldn't speak to the Director, it's a total waste of your time. The culture is set in place to protect the systematic abuse. To be honest the manager sounds like he/she has some sort of anti social behaviour disorder.
That said, I'm worried it will end up only hurting the people I
worked with. I've already heard that this manager has targeted someone
else, making their life hell. So would this be just a case of stirring
up a hornets nest? Would it just make the lives of my former
team-mates worse? I know of other complaints of bullying just being
swept under the carpet, even the person being bullied getting let go
You've proven this organisation is highly toxic and will leave a trail victims who feel scarred by the experience past and current . The company has put itself in a highly dangerous position for legal action should these victims choose to sue the company.
In the UK if someone is forced to leave a job due to harassment/ bullying it can be construed as 'constructive dismissal' click here to find a definition. I don't know if any type of law like that exist in your part of the world but there laws to protect employees for a reason.
We have organisations such as ACAS who give free employee confidential advice and help for any working situation (ACAS will only go to a legal route at the client's discretion).
Personally, I would reach out to my former colleagues even if its only to advise they do have options and external help that is available to them. They can make diary of incidents, dates, conversations, emails etc to show a pattern of behaviour of abuse perpetrated and systematic cover up by the company to protect the abuser. No such thing as the truth only what you can prove! If people collectively show similar or same targeting/harassment/coercion/bullying/cover ups it will extremely difficult for the company to defend.
If they want to do that great. If they don't that's fine too. They have to take responsibility for their own well being.
You have your new job and you're free of that place.
If you don't want to go down an advisory or legal route consider speaking to a career coach or a therapist to make sense of what you experienced and then move on from it.
All the best.