Using PCB after short-circuit
I'm not sure if it's my place to say this, but I think that you are treading a dangerous path.

This circuit is obviously AC-Mains powered and I don't see any form of isolation.  That isn't a problem for someone who has significant electronics experience but the fact that you can't deal with blown traces on a PCB suggests that you do NOT have the required experience to do this safely.

I'm not concerned about your ability to repair this unit.  What causes my concern is that you are connecting devices that eventually connect to other devices.  

For example, do you know what will happen when you plug the USB connector from your Arduino into your computer while both the Arduino and the AC Mains are connected to this board.  Hint: it involves lots of smoke, sparks, maybe even flames.  It may also involve electric shock.