While we're getting your replacement parts ready, I'd recommend you gather lots, lots of clamps. How many ? You can never have enough... Lots of those little 6" quick clamps work well for squeezing the wing into the rebbet on the rear of the baffles.
Don't use too much glue, you don't want it oozing out all over when the cabinets are clamped up. A nice bead down the center of each dado is all you neeed, it will squeeze through the joint . If you get glue all over the edges of the dado's prior to assembly, it will cause the dado to swell and make assembly a nightmare. The one exception is the rabbet on the rear of the baffle..... you want a nice thin coat on the 2 faces of this... use a small brush to spread the glue out ;;.. don't make it super thick... if you put a bit of extra here, do it near the corner where the 2 faces of the rabbet meet, that way when it is assembled the glue will be squeezed into the rest of the rabbet by the wings.
If you want to paint the base a different color, don't glue it on right away, only use the dowels/screws so it acts asa jig when you stnad the cabinet up and clamp it up. You can remove the brace after the glue dries , paint it, and reinstall with glue / screws .
I'd do the very top (wedge with single brace with hole ) brace last. As I mentioned in our emails, these things require a bit of filling/sanding to get really nice