Hello voodooradio1,
first of all, you are right about all the outputs being useable at the same time. But they will output the same signal, there is no loop on the Live.
The Line input cannot be used as an FX return, you have to choose between using the loadbox/SPKR input (with an amplifier) OR the Line input (with a preamplifier for example).
The SPKR THRU is a bypass, so you can send the signal coming from your amp (plugged in SPKR input) to a "real cabinet", for stage monitoring purpose for example. The full signal of the amp will be sent in that case, without any attenuation.
Th signal path is pretty straightforward in the Torpedo Live, note that the Line input will cut the Spkr input:
Talking about routing, an interesting option is to have a dry signal (no processing) on one SPDIUF channel, and the wet signal (with processing) on the other SPDIF channel. That's useful to record a dry signal and process it for example with the WoS III plugin in your DAW, while monitoring a wet signal processed by the Live.
