okay I finally got this baby working. quite difficult. if anyone wants any advice on setting up nginx as a friont-end proxy for apache2 ask me. I'm kind of an expert now :-) lol
now seriously, I can give you quite a few hints I had to learn the hard way...
i.e. *.domain.tld is completely different from .domain.tld when it comes to nginx :-(
still struggling with some smaller probs but all in all its working! seriously give me a few mroe days and I'll submit some corrections to that tutorial!