Dude, I feel your frustration. Not long ago, my 93 Runner had a parasitic drain. It took me an eternity to find it. Of course I'm an idiot when it comes to electrons! But I started disconnecting things, one per day, and would check the volts the battery had left the next morning and wrote down everything. Finally, I disconnected the alternator over night and low and behold, the battery was still fully charged! Even though the alternator was running perfectly, it had a bad diode or something. I replaced the alternator, and problem solved. I bet even though your starter works fine, it probably has a bad something in it. Disconnect it over night and check the volts the next morning.