The clue to me is that you found the initial timing retarded by 4 degrees, so somebody was trying to get it running right without pinging by backing the timing down.
First I would make sure you have the distributor stabbed correctly. Set no. 1 at TDC compression and make sure the rotor is pointed toward the no. cylinder (at the cap).
If not, the camshaft timing may be OFF, which can also account for you low vacuum readings. You'll have to pull the timing cover to verify that.