0. You didn't ask, but the first question is where to originate your trip. Most RTW fares vary by country of origin, Canada is now one of the more expensive. Cheapest origin is Egypt, Sri Lanka, Taiwan, Turkey, however none of those may be convenient for you and you have to add the cost of reaching the origin point.
1. Breaking in either TPE or BKK works well from Australia as there are much cheaper fares to YVR from there (even discounted business class)
2. A routes are limited but stable for now. Cant recall any new A routes being added but some have extra frequency in the past year and none were removed. Several routes are seasonal (eg. HKG-JNB) for A service. As for whether it is worth the cost, you have to decide that; it will be an extra USD 300-600 per A sector over D (depending on routing and fare origin). Lots of ways to upgrade D to A (using certificates, miles, upgrade credits) and if you are locked in to specific date/route it is sometimes difficult to get A inventory esp. on key dates like month-end or quarter-end.
3. OWE doesn't care about eastbound and westbound (Skyteam is the one that is awful about that). It simply isn't an issue, you can backtrack within continents an unlimited amount or between continents subject to the trans-ocean limits.
4. Unlimited transits/stopovers in any city (but obviously limited by the 20 segment total on the OWE fare).
5. October is the spring in CPT, not fall. Depends on your tastes and what activities you want to do, I like spring much better (but then I like to go on safari in the winter)
6. Under the current rules there are no advantages to the Star RTW products except if you want to fly to Star only cities and get FF credit on Star. Otherwise the OWE rules are much more advantageous. The fares do vary a lot by country though, so it boils down to question 0 (origination point). Also Star service is pretty poor in A for some routes, really SQ, LH and AN are the only good premium services and tend to be hard to book. Much easier in D.