Draining is the only way...but don't drain it dry. If you drain it halfway and refill, your CH will be down to 500 and that may be manageable. The water is a structural component. You may have to repeat the exercise.
Do not use Cal-Hypo type chlorine as it adds calcium. Bags of "Shock" are frequently Cal-Hypo and you don't want that. Never add calcium to your pool. Vinyl pools need zero calcium, no matter what the pool store says. Calcium's for concrete, plaster and tile pools, to prevent the calcium in them from being leeched out by the water. Not an issue with vinyl.