It could simply be FL studio displays it differently - Every note event with MIDI has two components, Note on, and Note off messages, which have a time - so a duration of it being on, and the velocity usually reslved as the volume of each event. Drums are dealt with differently. The note off isn't needed. The snare drum sample uses the note on and the velocity attached to sound, and the note off isn't needed - the snare has silenced already. So the pad is more likely to be where you need to look. Does FL studio have some kind of list editor? I suppose you've turned off the drums own sounds MIDI setup will have something like local off as an option. This should then only send the midi data. When you connect your drum sound to this inout in FL studio, does anything happen at all? MIDI activity light or real sounds? I guess as your posting it doesn't.
Are you able to record any data (assuming FL studio can show you what is coming out). What I could do is try the MIDI file you have recorded in my Cubase and see if I can spot anything) record any old drum stuff, even if all it appears to have are note offs, and then let me have it as a .mid file. I'll happily try it on Cubase, but maybe somebody with FL would be better?