If I wanted to make my own speaker cables, is this a good choice for wire?

As interconnects, why would you opt for side-by-side 16 ga. wire?  Are you unaware that opens up a world of RFI/EMI pickup?  The Jupiter wire is twisted…a better choice for unbalanced ICs.  For speaker wire, the Dueland might be fine at lengths up to 4M.  Beyond that, maybe go heavier.  For shorter, no need.

The problem with bananas, RCAs, and AC outlets has always been the need for a spring type elastic resistance, which copper is not very good at because it is a softer metal that deforms upon repeated loadings (i.e., plugging in and unplugging).   This is why most bananas, RCAs, and AC outlets are commonly made from an alloy of copper, which of course will be less conductive than copper.  Tellurium copper seems to be the best at about 93% of IACS (Copper is 100-101% IACS), while other alloys sometimes have much lower conductivity like Phosphor Bronze at 19% IACS.  Spades are different since they are actually connected by mechanical compression from the binding posts and have no need for elasticity, which is why it is not uncommon to see pure copper spades.

Interestingly, I thought the KLE bananas used to advertise being silver plated pure copper but after reading the technical write-up in their brochure, it was not so clear to me.  There is a lot of dancing around and referencing IACS but I did not see anywhere that they came right out and said exactly what the pin material is made from, except that it has silver plating and is apparently above 100% IACS in conductivity.  I am sure they are very good, but I get skeptical when I read a technical description that appears to dance around the subject.

IT DEPENDS!
Roughly 10 years ago Belden CLAIMED that a 'single strand pair' of their CAT5e Ethernet cable was capable of Audiophile grade transmission up to 10 feet.
That aside, we now have OFC, Long grain copper, Silver plated copper, Litz braided copper, and we haven't even started to discuss shielding or abrasion resistance. I cannot imagine using Cotton on anything.
I didn't see anything in your list that impressed me. What you discussed, I believe can be easily matched or exceeded by something simple like 'Cards 101' cable which is not too expensive and has great statistics. Now I am a huge fan of DIY but now in my senior years I have also given way to more abundant brands that can provide what I want at budget prices. The afore mentioned 1'01' cable can be purchased in any length up to 100ft and even at that there are options of running multiple lengths of that if you feel you need more size and 3 lengths could be braided. Options abound.

It appears the marketing department has hacked into the engineering department’s technical text once again! That Cardas 101 discussed by @esarhaddon does indeed look pretty good but I do find the write-up interesting in that they call the cotton filler material the dielectric and the actual wire insulation a “poly jacket.” Mind games.

Mitch2
What I think you may have missed is that I was jsut giving examples and possibilities. AS far as the cotton fiber goes , you might as well go demolish some 120 year old house and rip out the electrical wiring and use that for you speaker cable. Who knows you might get some good copper that way too along with the cockroaches and other creatures that love eating cotton sheathing.