Great trip report - I must say the plane looks about 71 passengers emptier than the one and only time I've flown Firefly on the usual Subang-Singapore shuttle route!
I am curious how the Firefly / Malacca Air collaboration works: does the latter effectively lease the plane and crew off Firefly, thereby bearing the cost of repositioning the aircraft both ways between Subang and Malacca?
Also, did you ask what the Malacca-Medan loads were like?