1) Red is speed, green is height.
2) Look at Sourceforge. Most of us play SDL, I think, but there's not enough difference.
3) If you are hungry, it should show in the bottom right-hand corner of the character description, on foot it will show you, it will also tell you you are hungry.
4) GH1: Eat by entering the inventory screen "i" and selecting a food item, sleep (not needed, heals and passes time) with "Z", you get hungry, but that is the only necessary upkeep, the Stamina and MP costs are all non-necessary, and you usually will regenerate them if you don't use them too much.
5) Are you happy? That could be a cause. Do you have cyberware, etc.? I've never noticed this, though I guess it probably happened to me.
There's no difference between the SDL and ASCII version beyond graphics and three or four characters of code.