This is awesome! Is there any support beyond the wrist, or how resistive is it when you press the buttons? Have you considered 2 hands too? Do you feel like you've maxed out the number of comfortably reachable keys? I guess you can't have keys off to the side since you can't move your hand relative to the keyboard. Does the thumb do anything currently?
I'm in this niche market too... although I don't really have an immediate use case beyond someday being more portable. Also had some issues with XR glasses and fov being reduced further by eye-glass distance.
No more physical support for the hand than what's seen in the vid. You can check more info in the github repo (https://github.com/akavel/clawtype) and on printables (https://www.printables.com/model/1231156-clawtype). The strap and the plate under the wrist seem enough that I'm not looking to improve on that at the moment; but I still need to test this version on some longer usage sessions. Interestingly, the original inventor and patent owner (https://web.archive.org/web/20220201061603/http://chordite.c...) has a design that doesn't even use a strap, but I didn't explore this direction yet (and honestly not yet even sure how to crack it). I know of another designer who's trying to iterate in that space: http://blog.russnelson.com/chordite
As to resistance, there's a balance to be adjusted between having the buttons too easy or to hard. This seems in main part to need to be adjusted by their positioning though. If too easy, you'll press combinations/chords accidentally too often. If too hard, it gets tiresome and annoying. Maybe there's some better placement possible, haven't found it yet. The switches currently used are Alps; they have dimensions which make them a good fit for this particular design; Cherry MX are a tiny bit too big and would require some rethinking.
As to 2 hands, the whole point for me is to have my main (right) hand available for other use, like drinking water, or otherwise supporting myself in the physical environment around. So I'm not currently interested in two-handed.
As to the number of keys - the four fingers seem busy enough; on the other hand, if you could fit smaller switches around (as in the DataHand design https://en.wikipedia.org/wiki/DataHand - see also 3d-printed clones on the internet - _edit:_ e.g. the https://svalboard.com, as mentioned by someone else, and lalboard https://hackaday.io/project/178232-lalboard-ergonomic-keyboa... as respectfully linked from therein), maybe you could try working with that. The obvious extra possibility is the thumb as you mention - it does feel like something could be added there, though it also sometimes helps a bit in holding the device. The original Chordite designer managed to somehow do it without a strap, but his reasons to not use the thumb are somewhat confusing to me.