Driving Relay to switch 6A
You need to focus on the coil data itself and not the contact data for the relay.  6A will be right against your limit for switching your load.  15V is well under 125VDC so you should be fine.  Just something to consider.  

At 5VDC, the coil has a resistance of 147 Ohms which means it will require ~35mA to switch the relay.  So the relay does not require 1A to switch.  It has a power of 170 milliwatts from 5 to 24VDC.  

By looking at the GPIO chip, we can observe that the maximum source or sink current by any output pins is 25mA.  This probably will not be enough to swtich the relay on and off.  Therefore, you will need some type of amplification to make your circuit working in between the microprocessor and the relay.  I will leave that up to you.