I didn't read anything in #12 or 16 that was constructive.
But, anyway, my question to you is whether you covered that initial base, sending 'data', in some fundamental form, from the Uno to the ESP. ('ABC', '123'); confirming that you can do that much first.
What's more, this subject is a code desert.
I guess you need to "post your code", the 'transmitter' (Uno) sketch and the 'receiver' (ESP) sketch.
Before you do that, be sure to read about 'code tags' so that nobody has to be a "code tag nag".
All about Code Tags (direct) --