Congratulations on starting a search for Sbarro pizza. I have persued other brands such as Round Table and Shakey's and Mountain Mike. I have learned from others on this site. Since you know what you are searching for I have a couple of tips:
1. See what the founder was trying to produce. In your case, the Sbarro family came from Naples. They were trying to produce family recipes. Suggests they were making Neapolitan pizza. Look at the recipes in the Neapolitan section here.
2. Look at crispy crackery recipes posted here. See what those elements are. You are NOT making cracker pizza.
3. Based on those two hints, make a few test batches. Lots. Suggest you increase the water. Cracker is dry, Neapolitan is wetter. Try a few New York recipes. Much more oil in some cases. I'm not saying it tastes like greasy cardboard. (That would be wrong).
4. Read web sites everywhere. According to the vegans, Sbarro used to use lard, but agreed to stop. Suggests they may use Crisco.
5. Scrape the tomato soup/grilled cheese topping off and use your tongue to detect salt, sugar, olive oil.
6. There were previous posts on the subject here including a reference to the omnipresent Tom L.
Good luck on your search and you will learn a lot and hopefully share a lot.