"......and is now on all computers in the house..........It's now on all computers that connect to the router in the house"
It sounds very much like your router's been hacked, or more precisely, your router's been hacked and its DNS servers have been changed. That would explain why when you visit facebook.com, the webpage you get is clearly the wrong one.
To try and solve the problem, log into your router and go to the DNS server settings for the WAN interface. You'll probably find a couple of rogue addresses there, and if you do, set it to the option to get the server addresses automatically from your ISP.
If you that's too difficult for you then reset the router back to its factory settings. Note that afterwards you'll need to set it all up again from scratch.
If you succeed and the problem goes away then post back and I'll tell you how to prevent this from happening again.