Critta - Hiding in the glass gap is perfectly normal - just make sure that the cardboard is tight in there...have you considered using 'weather stripping'? it comes in self-adhesive roles from Bunnings and seals the gap very well...
Regarding the biting - he is likely a little hungry - a
Spotted python that age should be able to take a fuzzy or hopper mouse (depending on how well he has fed and grown to this stage) - if you are not convinced he can go up a food size then try and feed multiple pinkies on your feed night...once every seven days is a good schedule for a young snake...
