there is an error you might want to correct: At 0 Health my ant disappears but the enemy ants still die and give me stuff....
Fixed in the build that just went up. The outcome of a fight was decided from strength alone, and health was only ever deducted alongside it, never checked. So at zero your ants stopped being drawn while the wave carried on resolving and paying. Health stops the fight now.
Thanks to both of you. "You can idle your dead ant for money" made it very easy to find.