I'm not really familiar with Berlin specifically (since most of your questions seem to be tailored around that particular city), but I'll answer your questions anyway.
1. Not really, but you can ask (although it's probably better to keep it to this thread, so we don't contaminate the entire forum with posts in English).
2. First of all, I doubt that your experience would be significantly different in other big German cities: it's not really an isolated 'market'. Perhaps you should also consider looking beyond Berlin, as pretty much all major cities in Germany are less than 5 hours away by high-speed train. And regarding your experience itself... you'll find many posts on this forum (from SDs and SBs) complaining about the same thing (i.e. how difficult it is to find a suitable partner).
3. Many Germans (especially the older generations) are very hesitant to actually speak English in a real-life situation, even if they can (and many simply can't).
4. Well, it's certainly not optimal, but as they say: 'there's a lid for every pot'. However, to put it bluntly: I think that your age and lack of German language skills will automatically disqualify you for many SDs. You can compensate for this with your personality and other qualities, but I don't think that it will be easy to find a 'high quality' SD.
5. Whatever feels right to you (and your SD): there's no 'right' or 'wrong' way to do things, it all depends on the preferences between the two people involved. Although I can imagine that most men would be eager to take you to the 'bedroom' as soon as possible.
6. I don't think that it's particularly common, but nothing stops you from trying this at venues with wealthy men (although I can imagine that there will be 'misunderstandings' about whether you want something in return or not).