Serious overheating!

[Austin Calise]

A few things that come to mind would be 1 a seized turbo shaft limiting the exhaust flow
causing the manifold to get red hot. 2 would be a clogged cat or both cats.
I would first pull off the maf to turbo inlet hose and see if the turbo still spins.
If that checks out I would drop the cat to down pipe connections and check for clogging.
Did you find what caused the coolant leak, heater core valve? As for the no spark
I'd check the distributor maybe some coolant found it's way into the cap?
If you have access to VAG-COM you can check your fault codes, that 
may tell you more.

               Hope you get it shorted out, Austin