But I don't know how to break it down any easier. In the PMs I guided you through and there are written instructions in the package too.
Plus, I guided you along the other methods,
@AphoticD 's OneWindowBrowser couldn't be any easier - download, it go to
https://m.youtube.com and that's it...and it works on my 500Mhz iMac.
As I said, I think the problem lies in your install, as every step along the way, nothing seemed to work.
At this stage I'd say, wipe the iMac, re-install Tiger and all updates, then try OWB - if still doesn't work there's a hardware issue.
Regarding an Emac 1.42 - yes, it's a considerable upgrade over your iMac. I've owned one and it's a great machine, with Leopard you'd be watching Youtube in Roccat or Webkit with no problem.
If Youtube is a priority, then you have to have a dual G4 or G5 for easy 360P playback in a web browser. For less than that, SMTube handles it fine - I have it running on my 800Mhz G4 iMac and it works fantastically...but the problem is SMTube won't last forever, Youtube keeps changing and it won't be able to keep up.
Again, here's my video showing what my 1.33Ghz Powerbook does: