Number of workers involved, how large where these structures,how long tanks and other equipment where produced? How many workers each facility worked pre-war?
Defensive strategy used, offensive strategy the Germans attempted? Which held out and which failed and at what cost?
Was there anthing similiar, where, factories became their own battleground, able to withstand repeated assault?
It really reminds me of WW1 fortresses designed for a seige attack.
Any good reading on the fight in the factories alone?
Unfortunately, I do not have an in-depth knowledge of the factories during the Battle of Stalingrad, but as no one has responded to this thread yet, I can offer some recommendations for where you might find some answers.
John Erickson's The Road To Stalingrad: Stalin's War With Germany, Vol. I is a very good and detailed account of the Soviets' war with Germany up to and including Stalingrad. It has a really interesting opening chapter discussing Soviet war games prior to the German invasion in June 1941.
Though less detailed, Antony Beevor's Stalingrad is a very readable account of the Battle, and does focus on some aspects of factory and house fighting during the battle. Likewise, William Craig's Enemy At The Gates has some good accounts of the fighting, though it is somewhat dated now.
Chris Bellamy's Absolute War is probably your best bet on numbers out of my recommendations. It covers the entire war for the Soviets, but obviously covers Stalingrad.
Hopefully someone better prepared to answer your question will come and help further.
EDIT: I just glanced through Bellamy's Absolute War and found this passage which may interest you (pp. 512-513):
'North of the Mamay Hill was new industry, a series of steel and masonry factories stretching north along the bank: the Lazur chemical plant, the Krasny Oktyabr (Red October) metal works, a bakery, the Barrikady (Barricades) gun factory and, finally, the Dzerzhinsky Tractor Factory. The Red October works, Barricades factory and tractor factory each extend for about a kilometre, parallel with the river, and are between 500 and 1,000 metres wide. ... When the Germans reached the Volga on 23 August it galvanised Stalin into further action. In the city, more than a thousand workers were mobilized into militia units to reinforce the Red Army troops, and the City authorities ordered every factory and industrial enterprise to be turned into a fortress.'
EDIT II: A further interesting passage from Erickson's The Road to Stalingrad (pp. 363-4):
'[on 20 July] Chuyanov [chairman of the Stalingrad City Defence Committee] reported back to Stalin and the GKO [Gorodskoi komitet oborony, City Defence Committee] about the measures they proposed to adopt. A certain amount had already been done, especially the attempts to improve AA defences, but to convert an industrial city of half a million people into a fortress was a different matter: in what was now a familiar cycle, the civilian population, at least 180,000 of them, marched out to build the rushed and rude defences, trenches, fire-points and tank-traps, laid out for mile after mile ...'
Sources
Beevor, Antony, Stalingrad, (London: Penguin, 2011)
Bellamy, Chris, Absolute War: Soviet Russia in the Second World War, (London: Macmillan, 2007)
Craig, William, Enemy At The Gates: The Battle for Stalingrad, (London: Penguin, 2000) (orig. publ. 1973 via Hodder and Stoughton)
Erickson, John, The Road to Stalingrad: Stalin’s War with Germany, Volume I, (London: Phoenix, 2000)