1st time using SAUA on any airline.

Decided to make a last minute trip SFO-TPE for my grandmother's 90th birthday, as our work schedules have miraculously cleared up for the next few weeks. We also realized that we have enough Chase UR points to upgrade all 3 of us to Business. There are still B fare tickets available but unfortunately when calling EVA they said there is no upgrade available for any of my targeted flights, and some of the flights even have a waitlist. But the agent was unable to see how many people are on the waitlist.

I then did my research and looked up the open seats on these flights on EF, and they are running anywhere from 49% (20 open seats) to 72% (11 open seats) occupied. In comparison, the EVA agent was able to confirm 3 upgrades on a flight that has RL occupancy of 18% (32 open seats), but it's on the morning of my grandmother's birthday party - the only flight that I can't take! All the flights also showed I=0 on EF, but it seems like that doesn't really matter.

So my questions are:
1) How do I get on the waitlist? I've read the wiki on using SAUA on EVA, but it's not clear to me that if an upgrade is not available, would the option to be on the waitlist be shown instead?
2) We're looking at T-17/18 (for departure) and T-24/25 (for return), what is the chance that we will clear the waitlist based on the above stats?

Thanks for the collective wisdom on FT!