At least you got your feet wet. We have the same problem with chips. We always buy a couple of cases and end up with most of them at the end of the event. We have considered buying bulk chips and throwing in a few with each order. Kraut is another issue, nobody ask for it except when you don t have it.
With the food booth we had different coolers packed. We had one for meat, one for perishables, and the other for drinks. We use the Coleman Extreme coolers and they work great. The meat cooler stayed by the grill and the perishables stayed by the prep table. We plan on using the coolers in the trailer the same way. With the freezer installed we will always have plenty of ice on hand.
To really be profitable you need to book events back to back or at least every other weekend during the seasons.  Most of our loss for the last two years was from having to throw out or give away dated and perishable items.