Vertical Headers Won't Work if Interrupted by Merged Rows

[winged-voices]

Hi,
As I write that title, it seems like an obvious problem (and an obvious reason for the problem) - but no one's brought it up yet as far as I can tell so I'm hoping it's also an obvious solution.

I'm trying to make all cells in the first column headers, however I've broken up the table with merged rows and (for obvious reasons), that interrupts the - in the second column. It won't accept both "-" and "<" in a cell in either order; it just breaks the merge and doesn't fix the column.

I tried using a CSS column style but this ALSO gets cut off by the merged row. (It does work, so my styling isn't the issue, but because of the method needed to styles to entire columns, it only affects one cell if I put it below the merged row.)

Table in progress below (the colors are not final, lol -- you can tell a lot of this isn't sorted right, etc):

As you can see, the dashes are just a visible column. Looks the same in Reading Mode, though for transparency this was taken in Live Edit wrapped in a sheet codeblock.

Any suggestions? Am I doing something wrong here?
Seems similar in some ways to #36 and a little bit like the reverse issue of #59

Thanks!!