The difference between the ohms reading could be related to temperature. .5 ohms as stated in the manual is at 68 degrees, so if your engine was still warm then that could affect you reading. The difference could also be in the meter. You must first turn meter to ohms and touch leads together and make sure you get a 0 ohm reading. Chinese multi-meters (aka harbor freight) are notorious for being wrong, especially when dealing with ohms. Also be sure you are using ohms, and not continuity check, which displays odd numbers and is not ohms. It sounds to me like the reg/rec is bad. You stated that all your voltages were even at about 20v, so that sounds good. If stator was shorting, then one or more of your stator wires voltage would be lower on the shorted coil. Clean all contacts, especially stator plug, with emory board (or fingernail file), and use dielectric grease in the plug, when replacing reg/rec.