While HDR is used to reproduce micro-patterns in brightness in such a configuration, I think CRTs would have been capable of HDR with appropriate control electronics since HDR requirements are basically: pixels can individually be set to very close to black and also to "pretty bright".
Very likely. CRT technology from phosphors to screen masks to deflection yokes were highly-evolved but there was still a lot of headroom for more performance and new innovation. Some CRT tubes where capable of driving much higher brightness than their controllers ever allowed.
It's unfortunate that CRT manufacturing wound down entirely after ~2010. While the size, weight and huge glass volumes where impractical for mass-market consumer media devices, CRTs also had unique capabilities modern display tech still can't match. With all the current interest in retro CRTs, I actually looked into what it would take to do small runs of ultra high-end HD CRTs for collectors, almost on an artisanal boutique basis. Unfortunately, it looks like the upstream manufacturing chain of many component elements also collapsed because there were no other applications for them. So, the start-up costs to make the first one would be pretty huge.
