Will this at all help to help diagnose and maybe even fix why FF eats so much memory? I keep getting out of memory errors in windows and see FF eating tons of RAM & Virtual, and have no idea which is causing the errors or how to fix it.

That sounds very unusual. Have you got any add ons installed? I suggest trying a clean profile to see if that helps.

Unless you have lots of content open that inherently uses a lot of memory, or something.

Nope, extensions are fine (as per about:addons-memory)

From sysinternals process explorer I see working set 1.6GB and Virtual Size 2.6GB with ~200 tabs open. Don't understand why the virtual is so big.