Since its "my property"? Or does this apply inside the property which my house is built on? Same as i can install IP cameras on my property, as long as im not targeting sum1elses house.
Im not sure but i think you will have to put up signs about the cameras.
I know ive been attacked by someone before i changed to wpa2.
Yes you can "defend" yourself by properly configuring the access point so that others are unlikely to be able to use it. You can further "defend" yourself by recording the actions of a trespasser and providing those details to the authorities (whether this is actual property [your yard] or logical property [your network]).
This will maybe be a long shot but if you act like a threat here in Sweden, and trespass on others property they who own the property has the right to defend theirself (its a very big chance im misstaking myself)