Hello Aggie94. "Will the brisket be ready in time for dinner"? HORRIBLE question. We have all heard it. I know folks need to eat but brisket has a mind of it's own.
I agree with cowboy11; we should a step by step. BUT! I do not agree that it is the "quality" of the brisket. YES! I do agree that if you start with quality ingredients the final product will be improved but the whole purpose of low and slow and BBQ was invented because the poor folks could only afford the crap cuts of meat. Let's face it; if not cooked properly a brisket is a worthless piece of meat! Like skirt steak ( fajitas ) if noy done properly it would make good shoe soles.
You are using an offset. I used an offset for years. I will not presume to know your method; I will tell you what I do. This is NOT "kosher" so to speak; it is just how I do it: I don't worry about the grill temp. So long as it is around 250-375 I leave it to cook. WHAT I DO is to move the brisket to different parts of the grill ANDI roll the brisket and swap ends every 1-11/2 hours depending on temp.. I have never used a therm. so I can not give you numbers. What I can tell you is a packer can be cooked in about 8-10 hours on an offset. Now I am not talking about "bark" and "smoke ring", Good eating, tender brisket.
Don't stress over brisket. Just turn it ( mabe baste it ) and relax. Brisket is not a throw it in and forget it hunk of meat.
Just my opinion. Keep Smokin!