I think at lot of that 1500 trillion will get netted out, and all of it is notional value. But your general inference is valid. Let's say the danger area is ONLY 40 trillion in defaults, lol. That's almost the size of the entire world's economy, which I believe is around 50 trillion.
To make matters worse, the world's economy continues to contract. Eventually this fiat based system is gonna bust apart, in either an uncontrolled spasm, or as part of a controlled bankruptcy. Let's hope it is the latter. IMHO, pipe