I'll have to say that I don't really like 6L shape but this is fabulous! I'm glad that You didn't sell that car! All those problems is just bad luck!!
I was just thinking that is it possible to fit this just 5-speed TDI gearbox?? It's should be much stronger and durable? And another thing! Have You checked how much engine is moving when You step to gas pedal?? If it's moving much that could be reason to snapping those engine mounts.
And one more thing!
How much You have take power out in this diesel now??