[souffle]

1. We fill ours with baked play sand from Argos but some people use the Charlie chinchilla bathing sand.
2. Baby hamsters need to get the cage with their scent in it so I would not clean very often and even then only do half cleans. If he uses the potty it just needs cleaned as required and the cage can be spot cleaned daily in any wet corners. The poo is dry and innofensive so don't worry about that. Ours get a full clean with some bedding returned maybe every 6-8 weeks and this has been been found to be the best way to reduce stress in hammies.
3. I'd just use the Fitch. We have some boxes we put in for them to trash and they do like some larger bits so we use some cheap loo roll torn up a bit for them to drag around and make nests with.
4. Two are fine. We find igloo type with no bottom are the best. It's easier just to lift these up.
5. I think the hammy you are getting was born in the rescue so he will be used to handling. I personally would just give him overnight and start handling next day. Babies often get a little skitty when they move home until they settle but it is a good idea to get him used to the general noise of the house right away and he will soon accept this as the norm and settle down with it.
Good luck and looking forward to meeting him