Jackie, I'm going to dissent with the crowd here. I do butts a lot, and always wrap/rest at "around" 195. The carry-over cooking, when resting, takes them to 200+. I've always found 200, before wrapping, yields a dryer butt. Crazy talk?? Maybe.
But, I'll explain my rationale:
First, the butt has a lot of internal fat and connective tissue, so it's hard to really "dry out," unless you have a bad butt (it happens, just like any cut of meat). Don't let one butt make your mind up about how they all cook. I smoke 2-3 butts a month, and have maybe 1 out of 10 that just isn't as good as the rest. You mentioned this was a boneless butt; I believe that's part of your problem. For pulled pork, you will never beat the bone-in Boston butt cut of pork shoulder. The bone does amazing things to the cook, and boneless butts tend to dry out more. Your boneless butt may have very well been a picnic cut, too, which is the lower part of the front leg. Much more tough, and doesn't work near as well for pulled pork as the Boston butt.
Next, brining is a good thing - good job! I'm not familiar with Alton's brine, but I know mine works well (at least for me).
Brine for Boston Butt
Alton Brown usually has some good stuff - I'm just not familiar with his butt brine.
And, the real magic happens, with a Boston butt, during the "stall!" That's when all that internal fat is rendering down into liquid goodness! That's also when the meat is tenderized. So, once it pushes through the stall, and starts climbing again, the meat is very close to its most tender point. Once you get in the 190s, it's done!
Bottom line recommendations: First, get a bone-in Boston butt from a good source (I find Sam's butts to be really consistently good, but you may go butcher shop). Next, continue your brining regimen. And, wrap/rest the next one at 195-198. You'll know it's tender when you remove the bone, after the rest. You just give it a little wiggle, and it should pull out clean as a whistle! Shouldn't have any trouble pulling it then!