Mcp23017 getting very hot within seconds

I don't really understand what you mean. I just ment that the pins should be connected properly.

If I look from the top down to the PCB, ignoring what is printend on my PCB and just comparing to the schematic you showed:

I get:
GND on A0, A1, A2, VSS
5V on VDD and RESET

And this is exactly what I would expect here.