the upgrade situation is extremely confusing, my understanding from a number of conversations with OnePass is:
A class seats are available to Elites traveling on Y fares, but since 3/1/99 H fares are not upgradeable before the 1-2-3 day advance period.
A class seats may be released to F class before the day of departure by the yield management computer system, so it may be worthwhile to call again after being told FC is not available.
Standby priority is based on 1. Elite status 2. Time of check-in 3. Companions to Elites have equal status.
According to the Elite literature Silvers can call for upgrades on the day of departure, but there is nothing written about standby. perhaps some of the Silvers out there can let us know how they handle it.
A wild card in the system is the gate agents, who have a lot of power in their little domains. An agent can give the seat of a last minute no-show to anyone they want and justify it by saying it was to "expedite an on time departure" I have seen it happen, from the first row of coach!
Remember that the rules are not always applied uniformly, I always pays to ask politely for what you feel you are entitled to.