No current transformer should be left open-circuit. OK, it does have an internal protection diode, it should be OK, but you’re relying solely on that. The c.t. is so small that you’re unlikely to come to serious harm if the diode fails, but it’s still not something I’d do if there was another way. Why not turn the circuit off, twist a bit of copper wire around the plug (tip & sleeve, the ring is not used) and then you can put the power on, knowing that two things have to fail before you risk trouble.
If you change the sketch to the 3-phase, you can recalibrate each channel and the voltage channel in the sketch, then you won’t need the 0.4 in emonHub because the correct values will come out of the emonTx. I suggest reading all the documentation and the notes inside the sketch first, so that you have an overall view of the procedure.