Technically you are setting the IP address to the physical NIC but setting it to a vmkernel port - the vmkernel then is connected to a virtual switch which in turn is connected to the physical nic. This is all created for you during installatioin and by default the first physical NIC will be connected to the that virtual switch.
You can use the second physical NIC for redundancy
Yes you will need a seperate IP address for the iLO card