8 hours in.. so far so good. :)
To find the right value, I just randomly tried some in what I thought was the right 'range'. I got pretty lucky and had it on the third try.
At 440k the leads were arcing, and it shut down.
At 220k it dimly powered on, then shut down.
At 330k it powered on and worked. However, the SMD resistor bank I made for it got a bit warm. Warm enough to start to degrade my nail polish. The old resistors were smaller in size, but they could also use the board itself as a heat sink. Mine are naked.
So I took it back apart and soldered the SMD resistors onto some copper strips to act as a heat sink. They needed to be a fair bit apart to work at the required voltage, so getting it to fit in the space available with sufficient clearance to avoid arcing required raising it off the board.
That's about it.
I've already gotten 10 years of use from this monitor. It's 1080p, great contrast, and DVI (which I can run HDMI into) so it still checks all the boxes.
If I get another one or two years out of it this way I'll be happy. The cold cathode tubes will likely die next.
3 days in, always on, no issues. Took it apart and looked at it. No change. The copper bits are doing a good job of being the heat sink I needed.
I think I got it.