Dziękuję bardzo, Pan Dariuś. I don't mind if I do ;)
You're welcome. I don't mind at all, and I'm glad I can help.
Now... the teacher in me... I hope you understand ;)
The thing with the first name:
Official form: Dariusz (I'd this is too official for every day speech)
Diminutive forms:
Darek (OK for anybody to use)
Daruś (affectionate)
Dareczek (mildly affectionate)
"Pan Dariuś" should be "Panie Darusiu" (vocative). "panie" + "darusiu" sounds funny, but not incorrect. Kinda tongue in cheek expression, since the diminutive and affectionate "daruś" is gently cancelled by "pan".
So, the expected forms would be:
Dziękuję bardzo, Daruś.
Dziękuję bardzo, Darusiu.
Dziękuję bardzo, Panie Darku.
Dziękuję bardzo, Panie Dariuszu.
Seems that you know me a little by now ;)
Heck, I know you're really working hard here. And you even include such nice, and unexpected touches as "itd.?" in your post.
Signed: Daruś z Kanady :))