Welcome to MySwissAlps.com, ETOSY! Glad to hear our website has been a useful resource so far.
Now, as for your questions:
1. All three passes you mention are suitable for your plans. Which one is cheapest, can be calculated as explained at www.myswissalps.com/tr ain/ticketspasses/prac tical/chooserailpass. Also, consider your own preferences when it comes to convenience. I'd personally prefer to use an 8 day Swiss Travel Pass (www.myswissalps.com/sw isstravelpass/price) for this trip, as it's very by far the easiest option and allows boarding without having to buy additional tickets on most days. In the itinerary you've mentioned, you'll only need additional (discounted) tickets for the Gornergrat, Jungfraujoch (up from Wengen/Grindelwald) and Titlis. The rest of your trips will be for free. But as mentioned, you'll have to decide for yourself whether this is an important issue.
2. No, the Swiss Travel Pass Flex (www.myswissalps.com/sw isstravelpassflex) is only valid on the free travel days you select. On the remaining days, there are no discounts. If you do need discounts on the other days too, you should choose the Swiss Travel Pass Flex Combi (www.myswissalps.com/sw isstravelpassflex/pric e) instead.
3. Yes, the Swiss Half Fard includes nearly all trips, including scenic trains and mountain transportation. Please refer to www.myswissalps.com/sw isshalffarecard/validi ty for details.
4. No, the schedules will change as of December 12 and as far as I can see they're are not available yet. In most cases there will only be minor adaptations, so searching connections for another date will give you a pretty reliable idea of what the trip will look like after December 12.
5. The boat dock is right nex to the Interlaken West station. In the timetable, "Interlaken West" is used for the rail station, and "Interlaken West ThS" (an abbreviation of Thunersee, "Lake Thun" in German) for the pier. Further information can be found at www.myswissalps.com/bo atlakethun
6. Sure, you can get off in Oberhofen. There's no direct train back to Interlaken West, but you can either take a bus to Interlaken or a bus to Thun, where you can change to the train heading for Interlaken. Details can be found in the timetable: www.myswissalps.com/ti metable.
7. You don't have to pre-order a boat ticket. Just buy it before boarding; there will be a ticket desk at the pier. Mind that you only need to do so if your rail pass doesn't offer a free ride over the lake. If your pass covers the ride, you can simply board and show your pass when asked for by the officer. Please see www.myswissalps.com/bo atlakethun/tickets as well.
8. There's no cog rail between Weggis and Rigi Kulm, but a cable car. It will run in December, and so will the cog railway from Arth-Goldau to Rigi Kulm. A link to the official timetables is included at www.myswissalps.com/ri gi.
9. If you plan to spend some time in Bern, you can simply combine a visit to the bear park with a stroll through the old town centre: www.myswissalps.com/be rn.