It is obvious the man is obese. (350 lbs.)
A "plastic" chair for someone that size is asking for trouble.
Additionally, he's not asking for $1 million, just medical costs and loss of wages.
However, he should bear some responsibility for judging whether that type of chair could hold his weight as well, and asked for a sturdier chair.
I would award him reimbursement for medical costs, but no loss of wages.