I am very concerned about what you are writing here.
I have definitely not been spraying with any kind of pest control - I clean with un-perfumed organic cleaners, so that is not the case. I wonder where that smell might come from! And I am arachnophobic - so that you mentioned spiders in the flat worries me even more. Furthermore I cleaned very thoroughly before you came - cleanliness is something I pride myself with.
The stuffiness: I left the flat five days before you came, and it was very hot and sunny those days without anybody coming to open the windows prior to your arrival. I definitely should have thought about that.
Finally - the flat is not "quite" central - it _is_ very central. You only have to walk 100 meters and you can step on a train that takes you to Copenhagen airport, and if you walk 100 m in the opposite direction you are at Möllevångstorget, which is the square where all the genuine Malmö restaurants, pubs and clubs are.
I hope that you still had a nice stay with me and that your review dosn't scare future guests off - this really is a lovely apartment and it is my home.