welcome to the addiction and congrats on your Rubi
Ok I have had my TJ Rubi now for 3 years.
The front diff oil leak is because of the inner seals. PITA to change. I bought a pair of tube seals for mine. These do 2 thing for you 1. Seals the tubes so no water gets into the front diff. 2. Allows you to add extra oil to the diff.
Exhaust.....I have no clue
They always seep around the oil pan. I just wash it off every once in a while.
Windshield.....I would venture that your guess is pretty good.
JEEP = just empty every pocket