Determining the amount of water to create a given pressure in a sealed container
As I understand your question, you are limited to a total volume of $\pu{1L}$ and you can only add water (which I assume should remain liquid) and heat to the system, and are able to monitor it's pressure and temperature. 

Your limitation is the vapor pressure of water at the desired temperature.

At $\pu{453K}$, the vapor pressure of water is $\pu{9.88 atm}$. At $\pu{9.95 atm}$, water boils at $\pu{456K}$. So, if you heat the water to $\pu{453K}$, you will have the desired temperature and be very close to your desired pressure. Or, you could heat the water to $\pu{456K}$, and you would have the desired pressure.  Or you could heat the water to a temperature between $\pu{453K}$ and $\pu{456K}$ to get some trade off of being even closer to the desired temperature and pressure, but with neither of them being exactly what you want.  

Again,this trade-off is a limitation arising from the constraint of using water to control the pressure.  If you selected a liquid with a higher boiling point at $\pu{9.95 atm}$, then you could select a temperature at which the vapor pressure of the liquid would be equal to your desired pressure.