The small model with just two players that have to decide the values for just one factor each.
You can use range(0;1;0.1) or even better random() with an automatic Monte-Carlo simulation for the input factors to test the possible developments of the game. Here you see 1000 simulations of a Monte Carlo simulation using random(). As it seems there is no escalation of values nor do they become negative so the model seems to be robust.
However, to make it more robust you could use within the actual formula of the factors that are influenced by the player's input something like:
max(lowest allowed value; min(highest allowed value; player's chosen value))
Don't hesitate to comment on the model on KNOW-WHY.net to ask further questions.