[Lil bastard]

The numbers you post are OK - except for the low battery onl;y numbers - how old is the battery? If 5 yrs. or more replace. If 3 yrs. or more, seriously consider replacement.

Battery has 6 cells each producing about 2.2 VDC - wired in series total = 12.0 - 13.2 VDC.

Bosch alternator produces 13.5-14.5 VDC.

Suspect battery, bad starter, or starter relay. Cannot rule out bad ignition switch also.

I don't believe anything is drawing power with the car off, other than those things which normally do. I believe your battery is old, sulphated, or has a bad cell which does not allow it to hold a charge. Age means nothing. You can buy and install a new battery, take the car out, hit a good pothole and damage a cell, it can happen at any time. Rare, but it does happen.

Cheers!