You will be fine with SAS. Assume on the shutlte about 9:00-9:30 at the latest (I think they start running at 8:00 or so). The ride from POM to FLL takes about 45+ minutes, depending upon traffic. Plenty of time for the 12:20 flight.
UberX or Lyft will cost you about $50+ compared to about $30 for the two of you on SAS - but you can leave earlier, don't need to wait for the van to pick up other passengers, and will enjoy door-to doo service. Is it worth $20+ dollars? Your call.