Feng shui question: is it better to take a step back than to stay at home next door?

It doesn't matter. Generally, the door is most afraid of going to the door, followed by the position of the door facing other people's toilets and water rooms. This is more or less harmful to health, and there are other unlucky things. Your 40 cm retreat is just to hide the wind and gather gas, which is harmless. It will be lucky to clean the door. If you want to do it in the future, you must open the door higher. Hardly. I'm afraid of hedging.