Baz,
I use Ableton and route my interface and other ins and outs using an audio interface. I route my audio from Ableton to jammr via BlackHole, and then from Jammr out directly to my interface for playback and not back to Ableton for processing as you are proposing. I have not tried routing the audio back from Jammr myself as i am new here but will try it out and see how it goes. I don't have experience with Soundflower as i understand it is no longer supported. BlackHole has 16 channels (more than Soundflower's 2 i believe) so it may be a better option if you are trying to use Soundflower right now to route audio two ways between two apps (the goal being to keep the audio channels separate).
Heres the link for blackhole:
https://github.com/ExistentialAudio/BlackHoleHope this helps. Cheers