I don’t think the dry rub the night before is necessary, but it doesn’t hurt. I usually dry rub just before I put the meat on. It’s not like an overnight rub cures the meat or anything. For something the size of a brisket, we’re looking at many days to weeks before we get that kind of penetration. An overnight rub will not make a mite of difference in flavor or texture, I guarantee. I’ve tried it, and it doesn’t make a lick of difference, at least in my estimation. For a cured meat, sure. You need time. A much longer time. For barbecue, a 12 hour dry rub vs a 2 hour dry rub is indistinguishable.
Texas crutch is fine. I try not to use it myself, but, if you will, as you say, let the meat smoke for the first few hours. It is said that it’s the first four to six hours where the meat absorbs smoke, and after that, it doesn’t matter. Not sure if it’s science or superstition, but I’ve always had better results with meat that has been smoked first, then finished later, rather than meat that has been taken up to temp, and smoked later.
I disagree about the temp. 250 is fine. I do my briskets at 275, if I can get my WSM consistently that high. I feel like the slightly higher barbecue temps leave the meat moister than the lower ones. YMMV. It’s barbecue, and everyone has their own way of doing things, but in my experience, slightly higher temps retain moisture better while preserving the gentle chew of the meat you’re going for in barbecue. Seems like the longer it takes, the prouder people are of their produce. I’ve done 18 hours briskets (at 200-225), and I’ve done 9-10 hour briskets (at 265-285). The 9 hour ones have always been better, in my opinion.