Christopher, well done so far.
And yes it appears to be a bit of a Raw vs Jpeg argument (or maybe Betty or Veronica, Betty is simpler but Veronica's wealth has more potential; neither is a bad date)
I have three enlargers; two are colour heads and are typically used with "combined filter" settings, but the blue/green enlarger that I have must be used as a split grade enlarger.
The split grade technique involves changing the time only of each of the components based on what the highlights or what the shadows look like.
The single filter approach more often leaves me wandering between changing contrast or changing exposure. I.e. do I want whiter whites by increasing grade or decreasing exposure?
I realize that experience at reading a test print will eventually lead one to choose which path to take.
but you have chosen a path and are doing very well, the third print is a great improvement.
The split print technique may also offer a more direct path to understanding the nature of VC paper, as opposed to putting the magic filter in.
The way individuals learn varies.
While one exposure is simpler than two, understanding and getting to that setting may be easier with split grade.
Michael's explanation is excellant, but the supposition that grade 2 is set parts green and blue may not be accurate, for example Multigrade instructions for grade 2 vary from 52Y/20M to 39Y/43M depending on make of enlarger.
My own Zone vi has a grade 2 result at a 30B/70G setting but only with separate exposures. 7 seconds green and 3 seconds blue is not the same as 3 seconds green and blue and 7 seconds green.
And papers yield different contrasts for same grades anyway.
The way individuals learn varies. You seem to be channeling split printing well. If you wish to simplify later, you will do so with great understanding.
Wow, as I was typing this you posted above.