Have a 1986 4runner 4x4 with 340,000km (canada/frigid US model) on the clock....lots of little things (of course) two things of concern

1) the battery light and brake light are illuminated...at the same time, Ebrake is off, means I have a short.
dash volt meter drops form 14V (while driving) to bellow half (approc 9V) so I have a problem. It was intermittent at first but now is on all the time. Unplugged the Ebrake switch, at the switch, no difference.
wiring diagram links the two lights with a diode and then I believe to IC regulator....

2) hesitation when wet...even in humidity...haven't done any research on this, probably need spark plug leads/destributor etc.

thoughts?
the charging issue is more pressing as the battery is now dead and the old girl won't start.