I have 3 pieces of chuck roast (2 bone-in, 1 boneless) that I'm braising. each is between 1.3 #-1.5#. do I time it for 1.5# of meat or 4.5 # of meat? the pieces are laid out in the pan side by side.
The basic answer with braising is "it's done when it's done." You will want that meat falling off the bone. It will take at least maybe two hours, but you will want to check internal temperatures. Time per pound to me is meaningless, so that's just a rough guideline. It should also be smelling up your house in a pleasant sort of way.
When slow cooking or braising roasts, one key is to bring the internal temperature up to 190, at which point the connective tissue breaks down and you get that delicious 'fall apart' tenderness. Roasting might take 5 hours or more at 225, braising will be faster, guessing 2-3 hours? Either way, checking every half hour or so after the first hour the first time you make this recipe will give you a good feel for the progression.