Elemental sulfur (dust) can help acidify soil if you have the microbes but the S will bind with your Mg and Calcium, if your saturation of ca is below 65 or so you will leach out calcium with S before any Mg, this is not the problem for you.
I would agree though as I have dumped 50 kg on roughly and 30 x 30 area to see if I could get the pH down for a chance to grow acid loving crops, problem was it didn't move the pH in two years aside from a couple 0.1 up, whereas where I did gypsum, potassium sulfate and rock phosphate (calphos and Spanish river carbonatite) the pH dropped a couple .01. I tried mixing in a few bales of sphagnum peat moss to bump up some organic matter at the same time (organic matter is 5 in my clay soil). Even with a cec of 14, calcium at 75% and Mg at 20% the pH didn't go down. Either I didn't get the sulfur where it needed to be for the microbes to turn it into sulfuric acid (this is my guess as I just top dressed when I should have tilled it in 6 inches) or there is another trick to it.
The only reason sulfur can lower pH is the bacteria than can process it turn it into sulfuric acid, it can take 3 months (in every aspect of ideal) to a year to see some change so it can also be easy to over do it and go too far, I would suggest working it in 6-8 inches if you are going with sulfur but do not apply more than once a year. If you're noticing your Ca saturation drop take into account your sulfate in gypsum if you plant to apply that, although calcitic lime is a great one to add when sulfur isn't needed.
Your best you try, to harm I and I, Aiming to kill.
But I love you still Cause you are here to make prophecy fulfill.