1. I dont see how that's possible. You're going to have to provide examples.
2. Merging results from multiple sources is complex and has been described in detail elsewhere, you will have to search for it.
In the next calibre release I will change the code to not run title case if the result has a language set and the language is not english. THat should help, but it will only work if google returns langauge metadata with its results.
3. That is deliberate. Lots of amazon titles have junk in parentheses, like [Mass market] or (Kindle edition) in their titles. So calibre will strip anything in parentheses. That means an occasional false positive, but, that is an acceptable price. In fact the very example you quote has the title: Beruf(ung) Trader: Schritt für Schritt zum erfolgreichen Börsenhändler [Gebundene Ausgabe] or series names like this: Before They Are Hanged (The First Law: Book Two) [Paperback]
Last edited by kovidgoyal; 01-31-2013 at 12:02 PM.