What is the max current for the EV3 I/O port's VCC pin (pin 4)?
As seen in the schematics, pin 4 of all of the input and output ports plus the 5V on the USB host port is connected to VCC5V/VCC5VIGEN, which is supplied by U23 (the analog/digital converter is also connected to this, but current draw for that is negligible). U23 is a TPS2041BDBVR which limits the current to 1A and has a continuous current of 500mA.
So all ports and USB need to be considered at the same time and must not exceed 500mA on average or 1A peak.