Pressure is a meaningless figure with regard to CO2 bottles. It does NOT indicate fill level, only room temperature. Pressure will not drop at a given room temperature until the tank is virtually empty.
1000 PSI is a VERY high reading, and tells me that you are storing your bottle in an environment with a temperature of 85F or so. Above 88 CO2 goes to a "super critical" state which one of it's unique properties. If you are seeing 1000 PSI at ordinary room temp in the 70s, either your gauge is bad, or someone at the fill plant is over filling bottles, which is extremely dangerous.
Only weight tells you how much CO2 is in your bottle. There is no other way to tell except to put it in the freezer and then remove it into the sun, and observe the frost line. This works on any liquid in a tank.
H.W.