On a side track, @Monika. What is your (or your team's) experience with RPG systems? I mean, it looks pretty obvious to me that you're going for some very classic and D&D-ish way of managing combat.
If that's your intention I suggest you to look at how D&D and similar systems did things (but possibly do it with the help of KRyan, Lord_Gareth, BESW, Magician, me or some other player who is disillusioned with the system and is therefore able to point you the problems of D&D's math so you won't fall in the same traps.