Hello Jadtiger, glad you liked the game. There are not many good games left like this one, in spite of many glitches.
As to your questions, here are my answers:
1) About exorcism. I was stuck here, too. I looked everywhere but couldn't find anything until I saw it here in the forum. It was hard to find. Anyway, you need to have the things mentioned in Father Frederick's diary. You must equip the rosary, have in your inventory the Holy Scriptures and Mandrake Potion (obtained from the alchemist & seer lady who stays in her house in East Glatzburg). These are also written in Frederick's diary. There is one other item you need to have, which is Holy Water. Since this is not written in the diary, I lost many hours to advance the quest..
2) Use PeterAlf's instruction on the wine.
3) Keep the foundation stone and the bodies of the dead girls for Act 3.
4) Don't worry about the door. After exorcism, all will be unveiled :)
EDIT: About the Foundation Stone, my bad. After some searching, here is what I found. This is what Fenixp wrote in another thread:
"... and as for the stone, you first need to finish the quest with sanctifying the antient temple, then talk to the monks that move there."
I guess I missed talking to the monks, too. I'll go there and use the stone :)
Post edited October 29, 2012 by Excolion