Personally Responding To A Previous Employer Who's Trying To Sue For Defamation, With A Counter "offer"?

I was wrongfully terminated by my employers for reporting a case of child safety issues, which could constitute as whistle blower retaliation. But it's been too long to contest it in court, and recently a post was made about it which prompted the employer to send a pre-trial warning requesting the deletion of the post, otherwise they'll move forward with legal action.

I'm considering to use their letter to me as a guideline for lawyer speak to reply, and request for them to pay my lost wages. In lawyer speak, I would say that if they don't, I'll open a complaint for their company with the State Labour Inspection office, which could result in a public case plus fines up to 300k for the amount of illegal things they've done. I've already paid for a consultation for legal advice with a lawyer but the cost of them taking on my case is insane.

The employer has a long history of similar illegal practices, including blanket NDA's in contracts that say employees cannot speak negatively about the school, they also sometimes add additional NDA's when firing teachers without cause. They also just recently lost a wrongful termination suit and had to pay the employee their lost wages.

Plus, the boss started a relationship with an employer way younger than them, which caused a divorce and the teacher to quit their job and leave the country. I would wager there's a lot more shady things going on there.

Do I have a chance of success or should I just leave it be?

Location: MA