[GSBoek]

That's your air conditioning drain tube. It drains condensation water from the interior. Perfectly normal.

 

[GSBoek]

It doesn't stick out of the firewall too much, maybe 2 inches max. It usually drains on the frame. It shouldn't normally run on the bottom of the car on the outside and it shouldn't leak inside the cabin. If the carpet isn't wet then it's not leaking inside.

Here's a pic:

 

[GSBoek]

The stub one to the left of the exhaust. The cable you see behind it is unrelated and is further down, it's the O2 sensor cable.

 

[GSBoek]

Space is a little bit at a premium back there so it's not unthinkable that they had to remove the midpipe to create more space to maneuver.

 

[GSBoek]

There is, but I don't think it's necessary.