Hi bibijcp,
Some suggestions for you. I'm not sure that they'll all work in your case but no harm trying.
1. Get pine litter for your chin, it's more absorbent than paper, and less of an ingestion hazard. They are available at most major pet stores.
2. Cover your pee pan with more bedding, the picture you have posted shows very little bedding and if I were your chin, I'll not use it too. It should be a depth of 1-2 inches.
3. Clean your cage everyday, it doesn't need the full works, but you can change the bedding, sweep up the poo, stray hay, and give it a quick wipe-down. It's a good habit to have also because then you can monitor how much your chin has peed and pooed - signs that will help you keep your chin healthy.
Your chin probably smells because he's stepping in his own pee and getting it onto his fur. I have one whose toilet habits are not the most immaculate, even her tail is brown from all the staining (she's an ebony), but the daily cleaning/dusting has kept her pretty clean and smell-free.
With regards to the temperature-issue, air conditioning is definitely preferable. But in my experience, it is not an absolute must-have depending on where the chin came from. Have you spoken to your breeder about this? I'm sure he/she would have advised you on what to do.