As I understand it now you first run through Hunger/Thirst, THEN Starving/Dehydrated AND THEN the maxHp damage kicks in.
Better to have max Hp damage tick at the same time as the Starving/Dehydrated bar; you should be dead once you're fully Starved/Dehydrated, not become a mummy first and THEN take Hp damage
I don't care much for having 0 str when both hungry and thirsty; multiplicative instead of additive, so it's 0,25 would be slightly more bearable I think. Perhaps have Str tick down at the same rate as maxHp, with a small up-front percentile/flat penalty. I get a little weak when I'm hungry, but I don't immediately turn into a vegetable when I get thirst+munchies.
So yeah, hunger system. The idea is there but you could/should tweak the numbers and mechanics some more.
Thought about having *any* potion FULLY restore thirst? That way you can "force" the player to quaff un-id'd potions. A clear reward, but with a nice risk (depending on whether you have potions/what they do).
Edit: Derp no wait, I think you didn't mean an immediate drop to 0 Str.
Also, the maxHp damage is permanent? I'd reconsider.