I go for 195 in the flat, and 200-205 in the point. The last brisket I smoked sat at 170-174 for about 6 hours (the stall). It took MANY hours for the flat to go from 174 to 195. When you reach your target temp, you can wrap in a double layer of foil and surrounded by towels, and rest up to 5-6 hours. Plan on at least 2 hours rest. The hunk of meat should be pliable and jiggly. Toothpicks are great for those who have an experience for "feel", but if you are not an expert, trust your thermometer. My thermometer has never failed me, and feel has corresponded to what my thermometer told me. I'm not sure when looking at forum posts whether it is EST or CST or Western time, but seems like your times are totally within normal. Hold at 140 only if you need to hold for more than 8 hours. Hold at 140 is a last resort if you have no choice.