You also need to be sure to turn off the WPS feature in the router since no matter how good a password you use this stupid feature will give it out and it is pretty easy to crack WPS key and you can't change he key.
If someone wants to DoS your wireless the really don't need any passwords. They can just use the same channel as you....It happens all the time just because there are too many people using wireless. There are a number of attacks against wireless most of which you can not even stop. The most common one just sends data out pretending to be your router telling all the clients to drop their connection.