Presumably, the predator-prey model has an equation that models a relationship. Without that, you can't do anything.
Yes, there is only one critical point, which is the one you found. I'm afraid I don't know what "solving the linear comparison" refers to. The tangent plane to the surface at that point is going to be for some constant c, because the surface is flat at a critical point. I don't know what else to say about it.