With a soft head mallet firmly strike the shaft bolts back into the lower legs, this will release the lower legs from the shafts. Finish unscrewing the shaft bolts and the lower legs will slide off. You can not repress a steerer tube. A crown is built to withstand one steerer press in. If a crown is pressed more than once the metal becomes fatigued and is unsafe to use.
Negative air is used to help soften the ride of the positive air spring.
It provides a plush feel to the initial compression stroke of your SID fork or SID rear shock. My 2K Judy and SID HydraAir forks sometimes develop some oil around the lower leg bolt. Your 2K fork uses crush washers that help seal in that oil. Occasionally, if the fork has been serviced and a contaminate has worked its way under the crush washer, you may get some residual oil leakage. It won t affect the performance of the fork, unless the leaking is excessive.