I would make R’ 2 × 68 kΩ in series. Each resistor will then dissipate just under 250 mW, so a ½ W component, with a 250 V or 350 V rating, will be suitable. (Note, the peak voltage of a 260 V supply is above the highest common resistor voltage rating, which is 350 V. This is one of the reasons for using at least two in series.)
That will make R = 784 Ω, so choosing the next lower value, 750 Ω should be fine.
That c.t. already has a burden resistor built in, so use the circuit here Learn→Electricity Monitoring→CT Sensors→3. Interfacing with an Arduino→CT Sensors - Interfacing with an Arduino but DON’T have the 33 Ω burden - you already have that inside the case of the c.t.
But - you might be making things complicated for yourself. Both the c.t. and the a.c. adapter have a phase error, and it’s the difference between the two phase errors that causes you to read the wrong power factor, and which PHASECAL attempts to compensate for.
The ZMPT101B and the ACS712 both have a very small phase error, so the difference between those is very small.
I would advise you to use either the a.c. adapter and c.t., OR the ZMPT101B and the ACS712, and not mix them.
You can read about the phase error for our a.c. adapter and the c.t. (the 100 A version - but that 15 A one will be similar) in the test reports in the ‘Learn’ section here.