Bro, there are a lot of different inaccurate temp/time combinations that work for cooking a good brisket. BUT, none of them replace the feel of knowing when it is done. It almost sounds like you are in to times/temps too much. Any meat, especially brisket is done anywhere from 185 to 210. It is when the meat is tender when probed. There is no set of rules for a brisket. Keep after it and cook some more to get the feel for it. Good luck!
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NB Bandera with mods
Weber 22 .5" x 2, 26.75" x 1
UDS x 3
Created "The Great Spam Revelation of 2011."