Yes, Yes, and yes.You said here "the Dayton mic is working perfectly well with Spectroid, Audio Tool and Sound Recorder"
Did you not check the operation of IMM-6 on the tablet? Also, you have confirmed that the IMM-6 is picking up sound reliably on the LG V30, right?
If the IMM-6 is recognized correctly, the app graph should respond to a light touch on the tip of the microphone, and not to a touch on the built-in microphone. (There is no need to strong tap it with your finger. A slight touch is sufficient.)
However, google (one android forum and reddit) samsung online "expert" have advised it's a TRS jack only hence my confusion. It's possible that plugging in the Dayton into the tablet isn't cutting the built in mic when I tested it on other apps, but the why does the Wiim app display "h2w" when i start tuning.
The V30 is definitely TRRS capable, and checked it in exactly the way your described. I've raised another ticket as requested by Wiim helpdesk, as they indeed did suggest rebooting the device, which hasn't fixed the V30 issue.