Directional Coupler Implementation

I'm going to use an RF coupler to feed the transmit into the receive (in a TDM system) to measure power. I'm planning on using:

http://www.minicircuits.com/pdfs/DCW-30-272+.pdf

For the external termination resistor, should I use a 50 Ω resistor?

I'm feeding 30 dBm @ 1.4 GHz into pin 1 (input), so, should I see ≈ 29.87 dBm at pin 6 (output) and 2.4 dBm at pin 3 (coupled)

yes. if its a 50 ohm device

Yes, it should be terminated with a 50Ohm resistor with minimum parasitics. Output powers are correct, however you may experience loss due to microstrip lines.