1.Rig up an explosive using fertilizer and the cash register(who needs money in an apocalypse?) and make a nice stockpile of weapons. Nail guns, hammers, shears, rakes, hoes, saws (chainsaw if they have it, please), etc. Maybe some traps if I can find the right equipment. Wait for either rescue or a door breach. If the door is breached, first goes the register bomb, followed by a last stand. I would say make a run for it, but there's really no where to run is there?
2. Is that meters or miles? If it's meters, I'd pick up the little girl and sprint that ************(yay being on the track team?), hoping the cop can keep up. If he can't, he'll be a good distraction. If it's miles I'd sacrifice myself to give the officer and the girl a chance to get out. Pointed metal pole is my weapon.
3. Are the zombies 50 meters behind the guy, or is the guy 50m behind me? If he's right behind me and the zombies are 50m behind him, I'd stop, help him up, cap any zombies that get too close for comfort, and keep on for the heli. If he's 50m behind me, fuck em, he's zombie bait whether I reach him or not. I keep going for the heli.