You're right. My brain translates stickers to be "SFO-JFK" stickers - I think in blocks of 6.
Actually, the site says right now that I need 0 upgrades to upgrade. That's probably a bug.
Finally, thanks for prompting me to check again, I found that 25E opened up since I last checked! Moving forwards...
As a PLT, your upgrades are free on Y fares. It's possible when they re-booked you, they put you into that fare class. And if not, I'd still put in for the upgrade, moving from a middle seat to business class on a transcon is worth it, I'd think.
That said, given the unlikelyhood of it clearing anyway, I'd avoid doing an early online check-in. That leaves you free to change seats. Some are held for airport control; once those open, folks may start shifting and you'll likely be able to improve.