250-500cc '11 wr 300 fork rebuild question (OC KYBs)

How does one remove the compression valve assembly from the lower fork tube? I've got the spring out and most of the oil drained (I think). The shop manual says to loosen, then remove the compression valve assembly before removing the cartridge and pulling the forks aparts to get to the bushings and seals. I'm able to spin the valve assembly with the ratchet and 12 mm allen head, but I can't get it out, so I can't get the cartridge out either. The valve assembly was tight at first, but now it spins easily using the ratchet. Sorry If I'm completely missing something; it's my first time rebuiding these forks. Lastly, the manual says each fork should be filled w/643cc of oil. I've only been able to get about 500 cc out. I measured the oil height at 120mm before draining for reference when I refill. It feels and sounds like there is a small amount of oil still in the lower part of the cartridge when pumping (slight gurgling and resistance when pumping), but I can't seem to get anymore out. I'm pretty sure I have had no leaks. How do I know when all the oil is out? I would think I shouldn't hear any gurgling or air, and that I can easily pump the cartridge up and down.

Any help is much appreciated!

No worries! Now that the bottom (allen) bolt is loose, the entire bolt and cartridge are spinning together... the bolt is not loosening. This is very common. Your options now are 1) buzz the bolt out with an impact wrench or 2) put the spring back in, turn the fork upside down, compress it a bit to "jam" the cartridge into the lower tube so it doesn't turn, and then remove the bolt. Then you can pull the cartridge out, spring and all. It can then be further disassembled on your bench. I hope that makes sense. "Next time," all you have to do differently is to remove that bolt/compression valve BEFORE you take the spring out!

For oil, it's best to ignore the printed volumes and just refill to whatever level you want. 120mm is a reasonable starting point.