I often make homemade pizza making the bases by hand from scratch. I'm going away with a group of friends and plan on making a very large batch of pizzas one night. I'll use a full 5kg (11 pound) bag of bakers flour.  With a pile of dough this large, would it need to be broken up into smaller balls while rising or is it fine to leave in a single large ball (I have a very large saucepan that would fit it)? I'm concerned maybe air wouldn't make it into the base of such a large mass of dough or that the weight would prevent the dough at the bottom rising.   Commercially, how are large quantities of dough proved? 
That foam is perfectly natural.  The foam is the result of meats natural protein composition. If you've ever poached eggs, or boiled lobster, or cooked a stock, you'll know that the water can become a little scummy. If you leave the pot on, that scum makes a white-ish or grey-ish foam that forms lovely looking rafts. That foam is made of water soluble protein.  In your case, you have wet sausage meat in a case. A small amount of that meat's proteins, mostly sarcoplasm and myoglobin, are going to escape from their cells and into the meat juice.  When the sausage case breaks, that juice, a mix of water and protein, is escaping into a hot oven, and the proteins are going to spontaneously denature, forming a foam much like scrambled eggs.  If anything, you should be happy- water soluble albumin foam is a sign that the sausage is full of proteins, and is definitely made of meat, and not, say, recycled chipboard.   Enjoy the sausages! 