I began my smoking hobby on the Weber Kettle using the indirect method. Your plan and method appear to be largely correct: cook between 225-250*, foil around 165* and take to 200* internal temp, rest for 1-2 hours and pull.
My first question regarding your situation is "are your thermometers accurate?" Given your numbers listed, I believe something is off by quite a bit. A 4# butt should take much longer to reach foiling temps than 2.5 hours at the cook temps you describe. The meat is probably blowing right through the connective tissue break-down phase (commonly known as "the stall"), which is probably why you had to slice the last one and will probably have to slice this one. My guess is your cook temps are much higher than your thermos are telling you (or the meat probe is way off). Check both by testing with boiling water, if appropriate for your thermos.
Actually, I find the Weber is quite easy to maintain steady cook temps. I get a 3/4 load chimney load of coals hot and divide them equally into the 2 side baskets. I add 8-10 coals about every 35-45 min and can maintain an incredibly stable 250* cook temp indefinitely this way. Of course, I also add wood chunks when adding the coals. Temps briefly plummet when I remove the lid to add the coals, but rebounds quite nicely. Which brings up another point; we have a saying around here: if you're lookin', ya ain't cookin'!" In other words, don't keep opening the lid to check progress -- that will lead to wild temp swings. Wild temp swings generally just make cooking times longer, but they can also keep you in the "danger zone" too long for food safety protocols (bacterial growth), so making sure everything is accurate is a priority. Otherwise, folks could get seriously ill.
BTW, the minion method is really a method of burning coals so they light gradually through the smoke, requiring less attention (fewer cycles of re-stocking your fuel). Just search "Minion Method" here on SMF and you'll get a ton of info on it. You might be confusing that with the 3-2-1 method for smoking those spare ribs.
Good luck with the finish!. Everything should be fine as long as your meat probe is accurate, your getting the butt to at least 165*, and not lingering in the danger zone for more than 4 hours before consuming. Regardless of whether you can pull it or have to slice again, the product should be really tasty!
This hobby gets much easier with practice -- and the results keep getting better as you learn more about how your rig reacts & behaves. Enjoy the Q this afternoon, and let us know what you find out and how it all turned out! And don't forget the money shot Q-view!