Hi,
you don't need external 5V.
Simply use the COM port of the AV2.
Unfortunately, the C2 COM and the internal COM ports A-F do not support DTR.
You can use the rts line for that, simply connect pin 4 of the switcher to pin 7 of the AV2.
In Simple Win tie a "1" to the rts input of the COM module.
Please provide feedback if this works.
Best regards
Crestronfreak55