I am a fairly newbie...only done 5-6 packers but nailed the last two.
I think you are spot on for your rub.
My method....trim all the hard fat and a little of the soft fat as needed...rub...smoker temp in the 300-350 range...fat side down...when internal temps reach 165ish remove point rerub point wiith a spicier/sweeter rub for burnt ends.....put point back on.... foil the flat....back on smoker....start probing @ 195 IT...don't pull until probes like butter... last two didn't probe tender until 209-213. Then in to cooler for a couple of hours. Burnt ends can go until you have the look and feel you like. Can't mess them up.
I think on my earlier ones..I was pulling too early and they were drier and tougher. I thought I was overcooking...not the case.
WSW 22... Weber Performer