Low CH is not a problem with a vinyl pool, but high CH can be. You can still grow scale, especially in areas with poor water circulation. It's like grow-your-own sandpaper. You can actually get roadrash if you knock your knee against the pool wall. With a vinyl liner, you can't attack it with a stainless steel brush, either.
So the question is: how did you test? Did you multiply by the right factor? And did you swirl by hand or with a speedstir? My CH dropped 200 points just by switching to using the speedstir. If you're really at 1000, I'm pretty certain your wrist and your patience gave out early.
If the CH really and truly is 1000, you need to deal with it. I battle high CH constantly, and above 800, it gets difficult to keep CSI in range. Just raise the water temperature and CSI jumps up.
Do you have hard water in your area? Test the tap water and find out. Draining 25% won't get you to 750 CH is the fill water is at 300 CH.
Second worry: are you chlorinating with powdered shock? Cal-hypo adds a lot of CH along with the chlorine.