The dryer sheets shouldn't make it worse ...they should cut the static down ..maybe try and wipe the bottle down again / but you're still getting too much variation to suit me. So something is still going on ....
Look at the Hodgdon website - they have a lot more loads using Clays and 1oz loads / but I gave you the load specs right off the website - about 12 responses up for 1125 fps - 1290 fps.
" As an example Hodgdon Clays ( 1 oz loads, REM STS hulls, WAA12SL wad, and WIN 209 primers - has a load at 15.7gr for 1125 fps ...the recipe I use: for my target loads at 18.4gr for 1235 fps and a 19.8 gr for 1290 fps ....so I'm well within the high and low tolerance for the powder I choose to use. "
The hulls you're using are fine - they use the same recipe as Rem STS hulls - low brass is common on target shells ( its all I use ). The only thing you'll find on those hulls - is they're thin - so they will start cracking after 5 or 6 reloads vs STS or Nitro hulls will go 20+ reloads.../ but there is no reason not to use the hulls you have.
As long as you are using a substitute for the WAA12SL wad you're fine - a lot of guys use claybuster wads ...and they're fine / you just need the one that matches the ounces of shot you've picked.
yes, you can substitue the chedite primers for Win 209 primers.
Talk to a local buddy / maybe they can give you a hand --- loan you 1/2 lb of Hodgdon Clays or something for you to test.../ but don't give up.