Any ideas why resistance would be less than 10k - I measure its less than half.
Are you measuring this in-circuit? In which case you're measuring a complex impedance network, or in other words, you're measuring across other components in parallel with that resistor. Therefore you'd need to unsolder one end of the component to test it correctly.
It's unusual for a resistor to become low in value, so that wouldn't be my first guess. But it's just a pullup resistor, the exact value in that location will make little difference to the circuit.
Bypassing R484 and/or R454 removes the fuzziness. I'll try replacing these two resistors and see what happens.
I didn't see if you mentioned if the video was OK on the 23 pin RGB port or not, my skim read may have been too hasty. But if the 15kHz video is OK, and the 31kHz video on the VGA port has the issues as described, that sounds like an issue with the 28MHz video clock. That is created by a phase locked loop (PLL, U481). This circuit is fairly sensitive, and it can be affected by corrosion damage from a previously leaked RTC battery. You'd usually remove components that are visibly corroded, clean corrosion from the PCB surface, and replace the components with new ones.
If there's not been previous corrosion damage, then the solution might involve a simple adjustment of the PLL clock phase. With the video artefacts visible, turn VR470 (beside the flicker fixer enable/disable switch) 1-2 turns in one direction to see it if improves. If not, turn it back to the original position, then 1-2 turns in the other direction.
Failing that, the PLL centre frequency (28.375MHz) may need adjustment, which involves making the PLL run open loop (J482 on pins 2-3), measuring either the 28.3755MHz output (J483 pin 1) or the output /2 (14.18775MHz at J483 pin 2) while adjusting VC470 for a free-running centre frequency as close as possible. Obviously you'll need a frequency counter for this, or a scope with a frequency counter. Then replace jumper J482 pins 1-2 to run closed loop.
A quick Google search just found this well written PLL adjustment guide:
https://www.tsb.space/knowledge-base/a3000-flicker-fixer-repair-and-adjustment/