I'd hazard a guess that if the OP ran the ChatGPT dunning letter by a lawyer s/he'd point out a handful of issues with it. The ChatGPT letter might best be used to brief the situation with the OP's lawyer but not actually sent to the former employer.

This is not legal advice but that letter is long as hell and ain’t no one ever going to read it.

“Dear sir,

I represent Mr. Client. It seems you may have neglected to pay my client his last two weeks salary, which is probably an oversight. But if it’s intentional, it might be illegal.

Could you and I sit down to discuss? If you don’t have time for a conversation, perhaps you might save a few minutes by mailing him a check at his address in the amount of One Salary.

Best regards, A Pile of Meat”