I'm the same, but add MP points does work.
trainer tested on campaign mission. working perfectly. In some instances, you may need to wait until your unit begins to fire a few shots before you turn the unlimited ammo option on.
Also, some people use this option along with the No Infantry Damage, to run into enemy territory and in some cases the enemy can no longer fire at you. then you can turn it off and attack the enemy and then turn the option back on after a few shots.
we aren't changing the trainer any further. The stamina option worked perfectly here, as well as fuel, etc.