OP were you ever able to find an appropriate keyboard? I also just started looking for a good ergo tenkeyless, but have not had any luck. I'm actually really surprised there aren't any good options online. I used the Microsoft 4000's for probably 10+ years and when my last one broke I found out MS discontinued that model and their newer sculps were not to my liking either.

I'm currently using: X9 performance which is good, but my mouse will regularly hit the corner of the keyboard during spirited use and I find that it forces my right arm to spread out causing discomfort in my shoulder over time. I no longer work w/ spreadsheets all day, so the 10 key can go if it allows better ergo for my right shoulder (I work and game from the same setup so my needs may differ slightly from yours)

I tried: Perixx which I do not recommend. The wrist rest is much too low relative to the keys forcing my wrist/forearm to flex upwards. I felt discomfort after only a few minutes and there is no stand/adjustment to raise the front of the keyboard.

I'm currently testing (and typing this response on): Kinesis but i'm not sold on the split keyboard design. On a connected keyboard, I can locate my left hand first and my right will naturally find its home, but not so w/ a partition that moves. I might make a wooden jig to connect the two permanently, but that only solves 1 of my 2 problems. While gaming I typically use the edge of the keyboard to locate my left hand so I don't need to look down, but I can't do that now because I will instead hit the macro keys instead.

HOWEVER, if you don't mind the split keyboard style and macro keys. This is by far the most comfortable typing experience I've ever had. I purchased the red mechanical switches (my first ever mechanical KB) because they are supposed to be most similar to the membrane ones and are quoted to be linear and quiet (though this is definitely louder than my membrane KB by a good bit).

Sorry for the wall of text, but I figured I'd join the conversation instead of creating a new post since it seems we are looking for the same thing.

All the best!