Interestingly, today is currently available for DCA (as of 7:20am). Both parks were available for today for most of yesterday evening (from 6:30 onward).
#1 It's varied, but all 2021 weekends have been gone periodically for awhile. For instance, this past Sunday, 10/10 at noon, there were no weekend days available for the rest of 2021, but then they re-added a whole batch for next week, so 10/23 and 10/30 were open for awhile. October has been 100% "sold out" several times, going back to October 6, but it usually doesn't stay like that for long.
The availability will continue to fluctuate as Disney adds/moves reservations in batches, in addition to people cancelling. I picked up Saturday 12/4 this week on a cancellation - it's been gone for two weeks. I have my eye on 11/20 and 12/12, as well as Christmas Day, and based on how things have worked so far, I'm pretty confident I'll be able to pick them up at some point.
#2 I suppose that depends on a lot of factors and perceptions. Presumably, you currently have days reserved (hopefully including weekends?), which are contributing value. A lot would depend on your willingness/ability to pick up reservations that open up as time goes on.