Zero: I'm not sure exactly what to make of your idea, but I like the look. I may use this to help with simplifying mine.
Simple is good. Remember that every minute you use to keep track of hit points is a minute you lose from having fun playing.
One thing that's the goal here...being high level does not give you more hit points.
Well, I guess that hinges on the meaning of a hit point. In my system HP is not health per se. HD more closely corresponds to health, though you could just replace HD with Con score or Con mod in my system and you've got a perfect correlation for base health. (You have to bonus up max HP to compensate.)
You get better at avoiding losing them, but your actual ability to sustain having people poke around in your belly doesn't get better.
Exactly what HP represents -- the ability to avoid having people's attacks hurt you in a meaningful way. My system adds gradation to that meaningful way.
However, since Fortitude increases, your ability to deal with that does.
I didn't actually read your hit-tracking system, but I'm going to guess here that you're making tons of Fort saves. So every hit now rolls three or more times instead of twice. (Once to hit, once for damage, once for hit location?, once for the effect save.) You've (possibly) doubled the number of dice rolls. My system just adds a bit of overhead cost to keeping track of important HP points. (Instead of dead, dying, disabled, healthy, full my system has dead, dying, disabled, injured, health, full, so you're scanning over six conditions instead of five and scanning is inexpensive for humans.)
Any attempts at making hit points increase by level, whether valid or not, are not desired as far as I'm concerned (though they're not necessarily bad systems, but they're not what I'm looking for anymore than a really good socket wrench helps when I want a screwdriver).
Except that my HP and HP in D&D don't correspond with what your HP mean. They've abstracted away (and I've kept abstracted away, though less so) the tedium of keeping track of individual body location damage.