I'm sorry for the problems you experienced. As you wrote, I tried my best to fix the issues you pointed out on your second day, like buying a brand new double mattress, two brand new toilet brushes and offer to send you a cleaning lady (at my expenses, of course) for extra cleaning (even if I was totally confident of the state of the apartment).
I totally respect your point of view and, as I said, I'm sorry that the apartment did not meet your expectations but, sorry, I can't accept words like "dinginess" and your statement about the house being dirty and dusty. Please, have a look at all the other reviews about my apartment.
Also, how can a cupboard be so "chaotic" to find anything? Everything is there: dishes, glasses, cuttlery, pans, pots etc. Gas leaking, are you serious? About all the rest, about the rooms, the furniture, the windows, the two bathrooms, you can see EVERYTHING from pictures. As I said, please have a look at previous reviews, many of them say "the house is exactly as shown in pictures".
"The appartment is located in one of the main streets of Viareggio". This seems for you to be a negative aspect while it's generally appreciated as a GOOD aspect by guests because you're right in the middle of the city, next to the pedestrian area, next to restaurants, pizzerie, shops, beaches etc. and you can just forget you have a car and reach everything easily on foot.
My apartment is no villa, I know. It's just a big apartment in the centre of Viareggio at one of the lowest price around. You will not find top of the art furniture but EVERYTHING is displayed on pictures. What you see is what you get, literally.
I'm sorry for your experience, it's sad when someone's not satisfied with what you have to offer but I just had to reply.
Without resentment and without irony, I wish you more luck for your net staying in Viareggio.