When I was in my 20's and early 30's I rarely thought about optimizing such things. I thought people who obsessed over Vim/Emacs were a bit odd. Now I'm one of the odd ones. I hope you never have a need to resort to such arcane arts, but if you do, Vim and Emacs will be waiting for you.
Switching to an ergonomic mechanical keyboard (kinesis advantage) and a keyboard-heavy workflow (vim) allows me to work as a developer.
I can tell how often I resort to using the mouse each day by the pain when I get home (I have a trackball on my left hand side and a touchpad on my right hand side to try alleviate this), thanks to not using the mouse all day I can often game for a few hours without too much trouble.
This isn't necessary specific to vim, however vim's modality and extremely expressive command language really minimize the amount of movement I need to do for any given action, no more emacs-pinky for me.
Before switching to Vim a few years ago I got a Comfort Keyboard to see if that would help. But after switching to Vim I find that I don't need anything other than a normal keyboard so far. I hope that doesn't change for the foreseeable future.
I hope you continue to find ways to improve your situation. It seems like things just keep getting better for those of us who need to avoid the mouse as much as possible.
As much as I wish you weren't in pain, it is a little comforting to know that there are others in a similar situation.
The main advantage of the kinesis for me is all the buttons around the thumbs and the fact it supports remapping from the device itself, so that whenever I am feeling pain I move keys around to alleviate it (often moving keys away from pinkies and towards the thumbs if I find myself using them often).
I have a windows,alt,ctrl and tab key under each thumb. Shift and backspace under the left, right and space under the right.
On my laptop I have capslock as esc but this doesn't help too much as my pinkies are quite painful to use after a while.
I use dwm, set -o vi for most of my terminals, and pentadactyl in firefox.
Haven't heard of Vimium; I have been looking for a Chrome equivalent as I prefer it as a browser, pentadactyl is nice but it has the issue that it currently doesn't support the use of ctrl-c which drives me insane.