Is there a video of Layne Staley's last interview ever?

Maybe not his last one ever, but pretty close. Try MTVs website they have a pretty extensive archive. And they played a pretty big role in AiCs years. Also look on YouTube the quality may not be great but it will be extensive. Also try Google and Yahoo, you may get lucky. The problem with Staley is he dropped off the face of the earth, he literally vanished and when he was found it was days after his death. But with how popular AiC is you will be able to find lots of stuff. It may not be exactly what you are looking for but you will still find lots of stuff.

I'm still searching as well!

Yes there is.

IDK!