Security issue with Password and 40 MHz Network

Installing and Using OpenWrt
6
  1. looks like a user error. As eduperez said

The admin password on the router is not the wifi password, each one is changed on a separate page.

You can post a screenshot of your wifi page settings. You should change the password there. If you know how to access the router via ssh, you can post the output of

cat /etc/config/wireless

  1. You are not supposed to be able to force 40 mhz channel width. If there is any other 2.4ghz radio in range on the same channels all standard routers will fall back to 20mhz operation to mitigate airtime competition.