How to stream quality audio without latency
The problem is, you're tyring to do everything in software.  

It's one thing to have separate output, but if OBS limits you to only two channels and your workaround is to use Soundflower to "mux" (multiplex) those channels together to conform to OBS, then you're inherently introducing latency.  The sound must be brought in on each separate channel, mixed together, then sent back out on another channel only to be read in by OBS then mixed in that, then output, you're using a tremendous amount of CPU cycles for something that should have been done "outside" the OS.

What you need is a mixer (it doesn't need to be fancy) so that you can combine the audio before bringing it into OBS.  You will get much more use and versatility out of the mixer than the software.