Jon, loved your video and the commentary is great. My trans has a high level of copper too, likely coming from the trans cooler/heat exchanger in the radiator leaching a bit of copper into the oil. I'm shocked to here that Blackstone didn't find water in the oil. It looks like rust to me.
I think ATF in a MTVR is fine. The 7 ton trans runs so much cooler than the 5 tons, which can easily get over 250 degree. I've yet to get my 7 ton to 200 degree.
I'm not one to give a lot of advice, but I would defiantly change the oil again soon. The oil that was in there looks terrible and only you know how it tastes lol.
BTW, you pronounced my name correctly at 30min in the video. Kudos