Looks awesome. Chuck roast is one of my all time favorites for the smoker. I got a couple in the smoker right now!
For mine, I don't marinate. I apply Head Country rub the night before. I really like Head Country on chuck roast - but any rub is good. Just about anything you can think of will taste great.
I put the chuck into a disposable pan like you have (or a regular one wrapped on the outside with foil) and smoke for about 6 hours at about 250. My smokers running hot right today - about 275 . .but that's going to be just fine. I don't check temperature with chuck . .I look for it to wobble almost like jello when I poke it .then it's done.
When the chuckies come out, there will be a lot of juice/liquid in the pan. I'll wrap the chuckies and place them in a cooler and set this juice aside. When the juice cools enough, I'll de-fat it with one of those "pour from the bottom" measuring cups. When it's time to serve - I'll pull the beef and pour in about 1/4 cup of my de-fatted juice and about 1/4 cup of bbq sauce (using Head Country today). I eyeball these amounts . .you want enough to coat the meat a bit but you don't want it pooling at the bottom of the pan . .just add a little at a time to get the right amount.
Then I serve as sandwiches with traditional Texas trimmings - sliced onion, bbq pickles and sliced jalapenos.
As you've noticed - chuck seems to come out great no matter what you do. In Texas, the land of brisket, I am the only one of my friends to does chuck but my chuck always gets eaten up . . .can't say the same for a lot of those briskets, lol. Unless it's from somewhere really special, I'll take chuck over chopped brisket any day of the week.
Another reason I love doing chuck roasts it's ability to freeze and reheat well. I always make a ton for the freezer. I put it in vacuum sealer bags. When it's time to reheat, I just pop the bag straight from the freezer into warm water to reheat. I fill my cooler up with 150 degree water and let it set for an hour or 2. Perfect every time!