File the FMLA paperwork. It does protect the job for 12 weeks.
Florida workers comp pay 66% when on a no-work status and roughly 64% for light duty. If his wages fall below 64%, comp has to pay the difference. (It's calculated by normal salary x 80% less actual wages x 80%, so it's roughly 64%).
Getting a lawyer in comp won't protect him from getting fired. That's between his employer and him.
But it is illegal to fire someone during the 12 weeks of FMLA. If that occurs seek legal advice.
If the comp doesn't pay lost wages or provide medical on time, call a lawyer. But for now, FMLA paperwork.