Following up for those interested. I had great success with adding salt last and in increments. I started by adding all the other startup chemicals, checking and adjusting levels as I went. (And yes, waterbear, you were correct – my plain tap water had TA 90 and CH 137.)
Then I added 2/3 of the suggested salt amount and the SWG indicated low salt. So, I added ¼ of the previous amount, and bingo, the magic blue light came on. The SWG is now creating so much chlorine that I’ve had to turn it down from 6 to 3 (also helped by the new presence of CYA, I imagine.)
Also, the effect of adding borate has been excellent. My TA and pH had been all over the place, but since initial adjustment it hasn’t budged from ~135 and 7.6 in two weeks.
Thanks for the help!