current drive capability of cyclone II EP2C20F484C7 FPGA

The 500 mA are not sourced from FPGA but from on-board voltage regulators. As starter board uses linear regulators, it may run hot with 500 mA load. (You should check if this a typical or a maximum current consumption). Maximum IO current load is specified in Cyclone II device manuals. Generally you have current capacity per pin for IO standards similar to logic devices and additional limits for pin groups at the FPGA, e. g. 100 mA sum for all pins related to an individual VCCIO pin.