Nice cook. Looks good. It's kinda hard to mess up a pork butt IMO. Short of drop kicking that some-bitch across the yard. The real issue is learning something so you can be ready for next cook. Temperature fluctuations...normal, but dropping to 90 isnt. Was it a fire issue? Temp probe placement reading wind coming in from top vent? Large smoke chunks prohibiting a smooth flame front?
Some folks here put some lump bits over the top of the snake to help the flame front stay consistent. Always keep top vent downwind cuz wind blowing straight in the top vent will have you chasing your tail riding the temp adjustment rollercoaster.
I personally run a 3x2 on a 26r. All vents WFO for 6hrs. I start at 6pm. Pull it off smoker at 12 and place in a foil pan and tightly covered with foil. Straight into the oven at 225-250 depending on size and how late I wanna sleep. Then remove from oven and place in cooler until time to eat. Remove from foil pan. Pour juices into fat separator. Place pork back in foil pan, shred, and pour juice, minus the fat, back over shredded pork while adding more rub to your taste.
I find this is the best way for me to:
1) get sleep so I can be sociable
2) turn out consistent, juicy, well flavored product
3) transport with the least amount of mess possible by removing the juice, shredding, and putting it back in.