Wiring diagram in a two-story wooden house
In general, the scheme is correct. On outlets larger than 16A, the machine cannot be installed. 6-10A is enough for light. RCD 10 mA - may falsely trigger, in this case you need to try 30 mA (I just warn about a possible situation). And why do 10 mA on the refrigerator? Less is better? On the water heater, I understand - you want to protect yourself as much as possible when using this device. Put 30 mA on the refrigerator.
The cable is basically correct, but it is better to put 4 mm² on the water heater. 2.5 mm² - almost end-to-end.