I wonder why you seek help, but not at least try to see if it’s OK before seeking more and more help about the exactly same issue? Isn’t it also a waste your time, as in last 2 months?
Please read the following paragraph in:
https://arduino-esp8266.readthedocs.io/en/2.6.3/reference.html#digital-io
Digital pins 6—11 are not shown on this diagram because they are used to connect flash memory chip on most modules. Trying to use these pins as IOs will likely cause the program to crash.
You are using in your code
pinMode(6, OUTPUT); // On définit la commande du relay de la chaudière en sortie
digitalWrite(6, HIGH); // On définit le premier état du relay de la chaudière à l'état Bas
and also 6 more of that, such as
digitalWrite(6,LOW); //On allume le relais de la chaudière
....
Just replace pin 6 (actually GPIO6) to D6 (actually GPIO12) for all related functions will solve the WDT reset issue.
And if you care to check the original code posted in
It’s using D6, not 6.