As someone who has worked on superconductivity I'd say that all of these are all potentially HUGE, but meaningless individually because they require experimental replication. They point to at minimum a new class of high temperature superconductors at least as good as current industrial ones. To know if it's truly transformative or not though we'll need multiple confirmations from big name labs. That's going to take time, so this trickle is exciting but won't mean much until the dust settles.
Another ARPES person! Totally agree with you, not only the density of states but the flatness of the d band at the Fermi level is extremely encouraging. The simulated results look good enough that even if they had come out first I think that they still would have prompted someone to synthesize this.
There are better, less destructive ways to test the transition temperature. Apparently LK-99 is hard to make in bulk, so they probably don't want to torch their sample.