still learning the runners, but anyway....the brake issue sounds more like you are losing power assist am I correct? Does it only happen in the winter? A leaking seal- fluid onto the rotors will not make the pedal hard up top, the pedal travel will remain the same, you just wont stop...Happens like that on Audis when techs forget to remove the gew they are sealed in...

The electrical issue sounds like a contact or circuit is opening due to heat expansion. I have seen cases where door seals and other gaskets, even metals expand causing (usually to close the circuit) the contact points to open. I am not familiar with the receiving "lense" or module on the 4runner so I do not know how that reacts to temperature. Guess I cant help too much on that.....

For the last question I think the first thing to do is to find out which type of fluid it is- engine oil, diff oil, or brake fluid and go from there....also make sure no one else is parking their leaking car there