Dear Mr. Chang,
I'm sorry that you did not have a good stay.
I can try to explain my position.
It is true, the apartment has little natural light that enters although there are many windows in every room. This is a normal condition for all the buildings in the historic center of Rome where the alleys are not more than 4 meters wide and the shadow of the adjacent buildings does not allow the light to enter.
The building where the apartment is located is from 1400, the ceilings are all made of wood, wonderful to see but it is normal in these buildings to see, (RARELY), some small wood bugs (absolutely not dangerous)
As for the problem of bathrooms, yes, there are small setbacks that can occur but certainly can not deny that as soon as you reported the problem, we intervened extremely fast to repair what had broken.
As far as cleaning is concerned, I can assure you that it is done carefully just before every guest enters the apartment. Probably the member of your group is allergic to something other than dust.
As for the price, maybe you have confused the numbers a bit.
I can tell you that for your group of 9 people you paid just over 25 euros per person, which is a price slightly higher than a HOSTEL on the outskirts of Rome.
For your next stay in Rome, I suggest to avoid booking an apartment in the historic center and to reserve a HOSTEL in outskirts of Rome, so surely will have a more light and will spend a little less.
Thanks for everything.