I/O confusion w/ MIDI controller and external host

Hello!

I understand that MuseScore is currently incapable of providing polyphonic feedback from a MIDI controller. I have (kind of) worked around this by using my MIDI controller in an external VST host (REAPER) and outputting the host's MIDI to MuseScore via LoopBe1. This way I can input notes in MuseScore while previewing them polpyhonically in another program. This, for whatever reason, only works if I open the programs in the correct order, i.e. MuseScore first, host second. Is it possible to keep this direct control and then use the external synthesizer to play back the score as well? I assume JACK would be required but I can't get MuseScore to show up on JACK's connection window. When I deselect "portaudio" in order to use an external synthesizer, MuseScore obviously stops responding to my host and, by extension, my controller. So I would have to use JACK to get the MIDI controller to control both the external host and MuseScore AND get the MuseScore playback MIDI to trigger the external host (see below for clarification). Is this possible? Any ideas?

MIDI Controller -> external host
while
MIDI Controller -> MuseScore note input
and
MuseScore score playback -> external host

MuseScore Version: 1.3
OS: Windows Vista Business
MIDI Controller: Edirol PCR-300
Hosts: Cantabile Light, 4Front piano module, REAPER
MIDI port: LoopBe1

Thanks!