I would think that a partial drain of the water would be best here mainly because of the liner age and shrinkage. If the liner pops out during or after draining you are most likely going to have to replace the liner.
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You can syphon off the vast majority , especially if you have some downhill away from the pool. Just get a garden hose started by filling the hose , then drop the drain end downhill at the same time you drop the other end in the pool , the water will continue to syphon as long as the drain end is lower than the sucking end or till it sucks air.
Or use a sump pump.
Yes, drained above ground pools are not structurally able to handle wind loads. The water helps the pool maintain its' shape.