Hey Mouseferatu,
Every post I've seen you make here you sound like a really insightful, cool guy- so hopefully you'll be open to the advice I'm going to give, even though (especially from your point of view as a game designer) it might sound insane....
And that is to completely relinquish the numbers of the game. Don't keep track of them. Don't have a character sheet in front of you at all. Of course you'll have to clear this with your DM, and make sure he's cool with keeping track of your character's numbers, but I speak from experience- this is EXACTLY what you need.
A few years ago, several of the players in a 3E game were metagaming so heavily they simply were mechanically chewing up numbers and spitting out responses based on calculations. These guys used to be awesome roleplayers, but somehow they ran into the same problem you have- and they realized they weren't having as much fun anymore. We talked about it and agreed I would take over keeping track of their character's stats- they only kept track of spells per day, and their equipment. They didn't fiddle at all with AC, HP, saves, BAB, skill ranks, none of that stuff. They knew what level they were, roughly what skill ranks they had, their feats, and thats it. During the game the DM (me) would let them know roughly how injured they were, but never gave a # of HP left.
What we found was that within three sessions, my players got back into their groove and put a lot more effort into their characters- developing personalities, background, motivations, mannerisms, etc. They quit worrying about numbers, feat chains, prestige classes, and probabilities, and put all that useless effort that detracted from their fun into trying to identify with their characters as more than a set of numbers. It was really worthwhile doing this, and now my players prefer it if I keep track of the numbers in ANY system I run for them since it frees them up to really get into character and visualize the game more. At least give it a shot for a few sessions- it will be hard to give up the numbers at first, but after a few sessions, its really liberating. I've tried it as a player too, and I loved it. Its definitely the way to go if you're wanting to distance yourself from metagame thinking and be able to identify with your character more.