This is the first time I ever heard him/you acknowledge the recent genetic analyses of yeast, causing separation out of S-04 from other strains. But I actually agree that WLP007 will give a similar beer to S-04. Not sure about 1098 though... probably still similar, but not quite the same...
I don't find temperature to have any effect on my efficiency. I firmly believe that you are seeing random data scatter, or the cause is something else.
A bone-dry mead will finish at 0.992 specific gravity pretty consistently, rarely any lower than that. You might only see this with a hydromel (low gravity mead) or when using a champagne style yeast that is capable of fermenting maximum sugars compared to any other mead yeast.
For mead, you...
You can ferment with any lager yeast at 16 or 17 C or even a little higher. In my experience, lager yeasts don't turn out as fruity or estery as people who haven't tried it will claim. And you'll get a result faster warm than if you fermented at cold temperatures.
Also, S-04 is an ale yeast...
Wyeast 2565 takes about 6 weeks to clear. That's not fast! Try any other yeast instead.
Kentucky Common is a great style. To me it tastes sort of like an English style bitter. It's one of the only styles from the USA where there's not a buttload of hops so it tastes like a "normal beer".
Yes, that is very normal. When fermented in the mid 60s F (that's about 18 C for you UK gents), my experience is that the S-33 / London / Windsor / M10 / M15 / Munton's family of yeasts (all very closely related) consistently completes fermentation within 36-40 hours max. If you fermented any...
I use my refractometer all the time. They are easy to use, but also easy to screw up if you don't know what you are doing. You need to be aware of a few things:
You need to keep it zeroed or account for it reading a little off zero using plain water.
Alcohol skews the readings but in a very...
There are many kinds of chlorine ions: hypochlorite (bleach), chloramine (stabilized version), and chloride (table salt). These are all chemically totally different, and Campden removes only the first two but not the chloride.
If I were you, I would split your batch 2 or maybe even 3 ways...
Hmm... 68C doesn't seem too hot. Not sure what is going on.
Regarding use of your refractometer, my standard guidance:
https://www.homebrewersassociation.org/forum/index.php?topic=28544.msg404366#msg404366