yes, i am aware of the other bootstrap pins. I took his statement to litterally, as if its part of the active flashing process like tx/rx pins But because GPIO2 is involved in the flashing/programming process, Did you go through the DHT12 code to see if the author messed up anywhere ? it seems he wr...

I am more curious why you need GPIO2 to flash your device.
GPIO0 is all that is needed.

your missing a button on the EN line to reset it after you pull GPIO0 low to put it into programming mode.
Your also missing a pullup on GPIO0. I believe there is a internal pullup but you'd have to check that.

Can this lack of bypass caps cause the module not to boot up ? Its hard to say every design and PCB is different. Also, is there any way to verify that my module is grounded or not ? I can't think of any with all the parts on the board. If the the ESP32 was the only part on the board you could use ...

Nothing jumped out at me besides the fact that you seriously need to put 0.1uf bypass caps on every power pin.
Maybe someone else catches something.

Try esp_sleep_enable_gpio_wakeup() in pace for your esp_sleep_enable_ext1_wakeup()

You can edit settings in menconfig

It would probably be a better idea to post that question over at their forum.

When you run those 2 (master & slave ) examples as is without any changes does it work fine ?

What IDF version are you using?