Yes, huge for fusion and would allow tokamak miniaturization too.

It would make fusion experiments cheaper, but not more successful.

It would definitely help with the commercialization of fusion power.

Why not? Higher temperature for magnets means magnets less susceptible to neutron flux right?

If this pans out fusion energy would be completely viable with enough investment. Right now tokamaks don't really have a pathway to being commercially viable and are basically 40 years away. For starters, If you can cut the cost by 2-4x you are right in the ballpark of what you would need to build a working tokamak fusion power plant. You would need to do better than that for fusion to be a viable power source but tokamak fusion was always only a magnitude away unlike other hypothetical fusion energy alternatives.

The limiting factors for superconductors in fusion power generation efficiency is the strength of the magnetic field they can generate which is limited by how much force the superconductor can withstand since the strong magnetic field induces enormous forces on the material. It also requires very high currents. This material seems fragile and can carry very little current.