Storage charge is only really needed if they will be unused for months.
To calculate rough charge time of a battery from flat you take the mAh of the battery and divide by the charging rate (mA) of the charger to get the time in hours.
Looking at the manual for your charger, its rated at 3A max (which is bull) so we'll go with 1.5A which is 1500mA
So take the mAh of your battery and divide by 1500 to get a rough idea of a full charge in hours.
Just divide that time in half to get a storage charge (if the battery is nearly flat)
Storing isn't really dangerous. Keeping them in a tin is good.
Charging is the potentially dangerous time so make sure to keep it on a baking tray or tin (without closing the lid) while charging and never leave it overnight.
A simple meter is good to get an idea of the charge levels.