The only other way I can think of is taking I-4 over to I-95, and go north that way. But it's a long way around to Wisconsin. You'd go 4-95-26 (pick up I-26 in SC), 40 (Ashville, NC), 75 (Knoxville), 74 (Cincinnati), 65 (Indianapolis)...from there, you probably can get home.
Most of the time, I-75 north in Florida isn't a problem. You said you left on a Saturday? Could it have been a day that the University of Florida Gators was playing a home football game in Gainesville? Or the Atlanta Braves was playing a night game at Turner Field? Or both?