@bnjroos Yes, the RX1 and RX2 delay are specified in the LORaWAN regional settings. I did not look that up for every region, but the ones I recall use 5 and 6 seconds for OTAA join, and 1 and 2 seconds for other downlink messages as default.
a) Yes, 2nd pin and 4th pin on the other side and are clearly labeled GND and G23
b) Yes, I'm using the same COM port with TeraTerm to run a script... So it must be the right one