Thanks!
The number of zombies you can evade and humans you can eat are actually based on spawn rate, which is based on how long you've gone - so the further you get, the more zombies spawn over time. This timer then counts backwards when you start as a zombie so the opposite occurs - less humans spawn as you go until the timer reaches zero again, then it's over. This approach worked really well in terms of the amount of time it took to implement, but it could be improved.
So to answer your question, I think you can potentially catch "about" the same number of humans as zombies evaded, but I don't think it's always the same, which I would want to change.
And yes I agree: some powerups, debris, and another sequence would be awesome! Maybe even a debris jumping/looting mechanic?