the black wire near the alt. is for your oil light,the sending unit is what you described coming out of the block
the in line fuse near the pwr.strng.resevior is most likely the source of your no start condition,you must have disturbed it while charging the battery,you should replace that entire receptical,but a simple bypass should be fine for test purposes
yes it does sound like you have a charge problem,it is most likely in or around the alternator
CAUTION!stay away from an old school test that requires disconnecting the battery while the car is running,one spark near a freshly charged battery could rip the skin from your face and leave a ringing in your ears for days