Avid Pro Audio Community - Question on digi 002r analog outputs

Currently I have my powered monitors (Solo6 BE) connected to the Monitor Output jacks of my Digi 002r. Sounds great, and I can use the front panel volume knob to change the loudness of the monitors.

I am also using the Alt Main Analog Outputs RCA output to feed into my computer's soundcard so that I can stream my music live over the internet.

I would like to have separate streams for each output; for example, I'd like to send a muted vocal track to the monitors and an unmuted vocal track to my computer, simultaneously.

I don't believe I can do this currently, because the Alt Src outputs are mirrored from the Monitor outputs. At least, I do not see any way to differentiate these outputs in Pro Tool's I/O window.

There are two ways I could split these streams up. First, moving my powered monitors to Analogue outputs (3-8). Or second, converting two analogue TRS outputs (3-8) into one stereo 1/8" jack

Option #1:
Moving my powered monitors to another output on the digi 002r. Can I do this? Would I go into the Main Analog Outputs (1-2) or the Analog Outputs (3-8) What is the difference? I would just need to be sure that the outputs I choose do not mirror the Alt Src outputs.

My mixes are plenty loud with the monitor pot rotated only 20 degrees. I read that the other outputs on the digi002 are essentially "knob 100% up all the time." So how do I not blow out my speakers if I connect them to these outputs? I don't have any other gear, with say, a knob to control the volume of the monitors. Do I just have, for illustrative purposes, -25 dbV set on my Master Fader in Pro Tools?

Option #2:
The other option is to keep the monitors on the Main Monitors output, and use the Analog (3-8) outputs to connect to my computer soundcard. The only input I have on my computer soundcard (P9X79 WS) is one 1/8" line in jack that I am guessing is unbalanced, -10 dbV. I do not have any digital S/PDIF inputs, or anything else that might be useful. So, in this case I would be trying to connect the Digi 002r's balanced, 1/4-inch TRS analog outputs (+4 dbV) into my computer's sound card (the P9X79 WS, which has one 1/8" line in jack, and once again, I am guessing is unbalanced, -10 dbV. To get stereo, I would have to take (2) x TRS analogue outputs from the Digi 002r and convert it to a single stereo 1/8" jack. Plus, even then there is a level mismatch. What can I do for this?

To recap, I want to send different streams to my monitors and my computer, simultaneously. I'll either have to move the monitors to Analogue Outputs (3-8) with no volume pot, or somehow convert two Analogue Outputs (3-8) to one Stereo 1/8" to feed into my computer.

Kindly,
kierkegaard