too plain, too edgy, too sharp, too bulky, and probably too pricy, how about no, lol

As explained above, RK9000 which is pretty standard layout, thus most probably all aftermart keycaps should fit.

RK9100 on the other hand using different last row as you noticed in the picture above.

It is almost impossible to find suitable spacebar.

For those keys on the left side, you should find 1.5x modifier keys as replacement.

IIRC, it is zinc.

LED circuit works separately with the keys circuit.

Btw, my guess is that the individual switch is faulty. Swapping it shall fix it.

But if your board still had warranty, it is safer and easier to rma it(actually switch swapping is really easy provided you had the tools)