I'm 6'7" 185lbs. Size 13 shoe. Almost all of my height is in my legs to. I don't have a bit of problem driving the Z. The seats don't support my whole upper leg so as a result all my weight is on my ***, so it goes numb rather quickly. I don't have a bit of problem driving the Z. However it grows very uncomfortable after an hour or so. After 2 hours I start getting extremely irritated and fidgety. After 3 hours rigor mortis has set in... I have to be removed from the car at that point by someone else.

I normally only drive 45 min at most, at a time. Not sure what i would recommend. Sounds like you have tried everything.

 

First thing to do, Stop bitching
2. move your seat all the way back, im 6'4 and im very comfortable in the car
3. Put the steering wheel all the way up so your knee doesnt hit. I know it "messes with your steering" but do it and save yourself from the possible clutch damage you might be doing currently, youll get used to a diff steering wheel height
4. I have size 14 shoes and i can down shift and rev match fine by half and halfing, basically use the inside half of your right foot for the brake and the outside for the gas to rev match, use your weight primarily on the inside to use for braking but still roll your ankle to the gas to tap the throttle and rev match, with some practice you can become very good at this,
The Z's clutch is very diff. from other cars but just give yourself more time to get used to how to drive it, its actually one of my fav. clutches just because i think you get a really good clutch feel with the Z.