Help with DC switch current
The current rating of the switch is based on the capacity of the contacts and is not related to the voltage rating. Note that when the contacts are closed and carrying the current, the voltage across the switch is close to zero.  The voltage rating is based on the insulation and contact spacing so as to not to arc over. Thus the 2 amp rating of your switch will not increase even if you only apply 4 volts (when the switch is open).