Well, this sounds unusual. I use Facebook every day and I never see these problems. Have you tried the following? Go to Help>Troubleshooting Information>Restart with Add-ons Disabled… Does this improve things? If it doesn't, you can also try "Refresh TenFourFox…".
Facebook works ok with my G4 (7450) in 10.4.11 (Tiger) I have had page render issues with facebook but in all those cases it was on facebooks end I had to open a support ticket and eventually they fixed the problem. Shelby I can think of 2 things to try 1. open a private window, Click File->New Private Window. Login too facebook and see if things load normally if not try and open facebook in safe mode, Click Help->Restart with add-ons disabled once restarted choose safe mode and try facebook again. I'm thinking it's facebook as I'm a popular photographer and use it daily and have my page not load or load half way and once I couldn't even make a post.
Shelby, it's best to test the add-ons one by one, then conclude which one interferes with Facebook. I use none of these. For downloading YouTube videos I use 'Download Youtube Videos as MP4', which is updated regularly and has never interfered with anything.