I always bend the retainers a bit to put more tension on the caliper it self and use much larger rubber elastics , if you do not use the rubbers the calipers will rattle like crap.
Yes, exactly. If the idler arm isn't moving at all when the bolt is torqued to 70 lbs, it means that the idler arm MOUNT is flexing (being drawn in by the bolt). The bolt is collapsing the mounting ears and pinning the idler arm between them.
Lowering the torque will free the idler arm, but that doesn't address why the idler is being pinned by the mount at the correct torque. My '72 manual lists the torque at 65 ft-lbs, but I'm guessing that's still going to be enough to pin the idler arm if 70 ft lbs does it.