I do agree that tokens should be handed less often and that they could not expire, but only for a current lifetime - after death all current tokens could be lost and player would respawn with 50 health. Infected or/and bleeding players would respawn as infected or/and bleeding survivor no matter how many tokens they had. Only exception is a player that used pills and infection is stalled for a while. An unforgivable punch to balls indeed, fitting the game description.
Players that survived a wave with less than 50% health could 'regenerate' the health up to 50hp before a new wave of hungry zombies comes for them. But what about tokens? Players with one token would ignore the 'regeneration' thing, but instead, they could get 50hp back, and two tokens could heal player to the maximum. If player was infected or is bleeding, the first token would be used to remove these negative effects while other remaining tokens (if any) for healing or in case there are none remaining - the default healing up to 50% would be used.
I know it's not perfect, but in my opinion, with a couple additions and corrections it could do well.