I take it you got the mount figured out? The motor looks pretty straight to me from the pics.
I just trim the dust cover to fit, some just get rid of it but I figure something is better then nothing.
Coaster Brake Dust Cap Mod
What problems are you having with the break arm? It just takes a little bend to clear the mounting bolts on the sprocket. You could also go with some Flat head bolts on the sprocket to give a little more clearance for the brake arm but not necessary if you bend the arm enough. You basically want to bend the brake arm in kinda of like a "Z". That way it is easier to attach the arm to the chain stay.
I will post some pics for ya in a minute, need 2 find them and re-size