Tuesday morning, Miami traffic?
You're taking a big risk. We have horrible gridlock some days but I guess if you made sure to take the express lane you'd probably make it OK but may get there a little stressed. If it's raining, ay ya ya.
Ft. Laud cruise terminal is about 30 miles from Miami. Ft. Laud cruise terminal is about 1 minute from FLL airport. Any chance you could change your flight? FLL airport is a much easier airport from the cruise terminal IMO.