First of hello and welcome dude. Have fun.
(1) Cloak etc for Kettenrad is a doctrine ability. The doctrines are not in yet so at the moment so there is no way to cloak it. But It will be in some time in the future.
(2) When you have enough PP (You get 3 per game win or loss) to buy the advantages they will be permanent.
They add the stated amount to your supply pool.
(3) Units that are successfully retreated of the field survive and retain any veterancy that they achieve. The death of a unit in game gives you refund in their cost when you return to the launcher.
Your supply pool only changes when you get advantages. You should spend as much of your supplies as possible. There are a number of guides that people have written to help you noobs, these will be very advantageous to you.
A lot of good guides are in here:
http://forums.europeinruins.com/index.php?board=34.0Remember you
will loose your first couple of games, it happens to everyone. Ask for hints and tips for team mates and opponents when they are not ass holes.
Even if you don't have a mic join the Ventrilo server its really useful:
http://forums.europeinruins.com/index.php?topic=7113.0http://forums.europeinruins.com/index.php?topic=8636.0(The download for vent is on the left panel near the top)
Good luck man and have fun.