From what I have read on here, ATL-SEA is a tough upgrade on a very elite heavy route. And the fact that it's a Friday will make it even more difficult, especially on a T-fare.

For your other question about why there are seats available but the upgrades haven't cleared - that's becoming the new norm: holding back upgrades until just before boarding - BFUG: Battlefield Upgrade.

Not saying you won't get upgraded, but don't hold your breath either.