Hi,

You are doing a lot with Serial already so it might all depend on what you are doing.

1)

If you are simply sending messages (from the Arduino Serial with line terminators) then the debugger can share the Serial port. If your code uses Serial.available() and Serial.read() then then you can only use the debugger in "Trace Only - No Break" mode.

That applies to any connection regardless of port or pin. 

2)

For SoftwareSerial if you are using that already it might be a problem but probably okay but again in Trace only mode. You will read in the following documentation how to change the Port, Pin(s) or Speed for debug.

SoftwareSerial can work with one pin for Trace and a second pin if you want to break or update the values of variables during debug. The pin or pins you choose must comply to the the SoftwareSerial specification where applicable.

I hope this starts to help you. I realize it might not entirely answer your questions so feel free to request clarification. 

Thanks