the battery terminal being loose would cause that, since the rectifier would freak out. the leak you speak of is probably not eh head gasket ro you would have compression problem with amount of oil that can run down the bike. It sounds like a corner on the valve cover gasket or something I think there is a cover for the valve adjust ment there so check it out the gasket may be worn. no biggie get a new one.
help this helps
This may help.
This sounds a little scary...
.. Seems as though you may have cracked the head deep enough to get into the actual internal cavity..OR the threads and their pilot hole went too deep into the head and got into the internal cavity..
ANYWAY.. its time to do some "exploring".. do not crank the bike again until you get the help of a qualified professional!!