Given your late arrival time, you might try Enterprise Rent-A-Car. Their location at the Orlando airport closes as midnight 7 days/wk:
http://www.enterprise.com/car_rental...id=004&cnty=US
Drop off at the Lake Sumter location could be done the following morning after you're in TV as they close at 5 p.m. M-F:
http://www.enterprise.com/car_rental...id=004&cnty=US
Hope that helps!
Bill