So here's some information I'm scrounging from the internet ethos for us. Here's some of the advice I've found so far about doors:
"The one that gets knocked off its hinges can be really easy if it swings upstage--just use loose pin hinges and have someone pull the pins just before the big moment. If it needs toswing downstage, you could use lift-off hinges so the actor just lifts the door slightly to pull it off its hinges. Likely need to modify the hinges so the pins are shorter and leave a bit of extra clearance inside the top of the door frame.
For the other door--what is it supposed to look like? a residential hollow core door? A solid raised-panel door? Probably the easiest and most convincing method would be to build it as a hollow-core door with balsa facing and just reface or rebuild it for each show. You could also build it as a solid door and pre-break parts and insert thin dowels across the breaks to hold the pieces together--that way when the door gets hit the dowels snap and the pieces fall apart. Or you could do a hybrid of the two methods, for instance build a raised panel door where the frame is pre-broken and doweled and build one of the panels from balsa so it can be destroyed each show and a new panel slotted in."
And for breakaway walls, I've found these videos to be pretty helpful:
Also my favorite guys at BFX made a video: