Those last two aren't fool proof - someone skilled and persistent enough could still slip in, but most anyone just looking for free access will look elsewhere. If they're still getting in after all this, then you're going to have more success talking to them than any technological solution on a normal home router.
just do the WPA. That will do the trick. I also limited mine to like 6 addresses (I have now pushed it to 8 with phones and tablets and itouches and rokus). I use a simple password that is hard to guess so I can tell people who come over if they want access. and I check it from time to time
We'll be back right after order has been restored here in the Omni Center.
That the universe was formed by a fortuitous concourse of atoms, I will no more believe than that the accidental jumbling of the alphabet would fall into a most ingenious treatise of philosophy - Swift
This thread goes through a sneaky way of replacing the login process with the command prompt in order to create a new admin account. This may work for you. https://www.howtogeek.com/222262/how-to-reset-your-forgotten-password-in-windows-10/