Air Malta (KM) serves the route twice weekly non-stop ...

Departure : Malta to Tunis
Flight Number
KM 680 thursday Dep:05:45 Arr:05:50 From:20/08/2009 To:22/10/2009
KM 680 sunday Dep:21:00 Arr:21:00 From:20/08/2009 To:18/10/2009

Return : Tunis to Malta
Flight Number
KM 681 thursday Dep:06:45 Arr:08:45 From:20/08/2009 To:22/10/2009
KM 681 sunday Dep:21:55 Arr:23:55 From:20/08/2009 To:18/10/2009

All other solutions are far more time consuming and due to only 3 days in Malta out of question anyway !!!
Even the Air Malta flight schedule is very unconvenient !
So, i really recommend staying in Malta or make a hop over to Gozo island (frequently served by ferries and seaplanes)