1: The calculations are not too accurate but the main thing is that just the resistance IS the main problem with speakercables (resistance kills dynamics). The (stranded) conductors internal interference is the second most important.
2: First part is correct. We can reduce serial resistance until it is negligable, on a insignificant level, beyond that it`s nothing moore to gain. But wow how much power, control and authority that can be recovered. You will only find a part of this by using huge stranded conductors because of all the internal loss. Heavy single-core performs in another league.
Your view on tubeaps is based on calculations which cannot allways be trusted. My claim is built on real listening experiences by both the tubeaps owners and me. No calculators involved.
Want to try the optimal conductor? Try mimimum 7awg solid copper to the woofers, use bi/tri- wiring when possible, thinner wires like 9awg to mids, 12awg for tweeters (if they are) alone. Be aware that solid conductors needs a short high-power burn-in to open up.
No b4icu, I`m not selling anything, just guiding thos who wants. I know how to make the ultimate interconnect too, and powercables. And moore.