Welcome to the site.
Be sure to update the loaction in your profile. Where are you living now? I'm just south of BR.
1-Yes, Open carry is allowed without a permit in La. This is a little known fact that La Open Carry Awareness League has worked hard to get out to the public.
2-I don't know the specifics of the Peacable Journey Law but in La you may transport your firearms in your vehicle loaded and placed anywhere you wish. There is no law requireing that they be unloaded or stored in a compartment or case. Some people use the term "extension of your home" when refering to vehicles and carry or transport of firearms or self defense.
3-If you believe your life, or another persons, to be facing grave bodily harm or death you may use resonable force to stop the threat. You can't blast away at someone breaking into your car in the driveway or fleeing from your tool shed. You can shoot if they are forcing their way into your home or trying to jack your car while you are waiting in traffic.
It's great that you want to get educated on the facts. La Open Carry Awareness League has some great info in it's forum (and soon to come on it's new webpage). Check out the info there at www.laopencarry.org.
As always, This is not legal advice and is presented for informational purposes. Do your own research and consult a lawyer.
Steve Raacke, Secretary
La Open Carry Awareness League