Is it safe for me to put my foot into the foot stirrup when using the ACUdraw or ACUdraw PRO cocking devices?

No.  Do not place your foot in the foot stirrup when cocking your crossbow with an ACUdraw or ACUdraw PRO cocking device.  In the unlikely event the string-claw were to break away from the draw cords, the claw could injure or possibly break your toes or foot from the impact or cause other personal injury and property damage.