Regarding the cat airlocks, I wish more people would do that and be responsible with their kitties! We've also designed in airlocks on all external doors, not only for insulative properties but to make it easier to keep our girls inside where they belong
I'm sorry to hear about your kitty getting the tumour, but be hopeful: one of our cats was diagnosed with a nasal tumour and was given about six months to live; it is now 18 months later and if you didn't know you wouldn't even be able to tell she had anything wrong! We're hoping it is her good diet (fresh meat and Eagle Pack) and daily cuddles that are keeping her healthy