I wonder if you have fully released the kingpin top nut with grease nipple. If so and with bottom plate fully released and stub axle resting on lower cross tube end, you should be able to withdraw kingpin downwards.
After withdrawing kingpin on my Roadster there was the very smallest amount of residual tension in main spring. The advice from SSL, since it was their RS kit I was fitting, was to cover the spring and surrounding area with an old blanket then work spring off its seat. This turned out to be a drama free task. Make sure stub axle/disc assembly is well supported though to avoid straining brake hose.
ETA: posts crossed, looks like you're sorted now
