RE: Re: Temp measure at the point or the flat?
I always check dead center of the flat, usually just under the edge of the point. I can't explain your long hold @ 140, I never probe anything until I think it should be getting to 140-150 or so (saves probe wire spagetti knot mod when rotating stuff).
After going an hour per pound, you should start being able to check by how much resistance you feel when inserting the probe. If it goes in with little resistance (like checking a done baked potato) you're there. If it requires a little force, needs a bit more time.
Sorry there wasn't more help at the hour you needed it Bro. Hope the brisket is good.