I don't have a chameleon yet, but i want to be prepared and have done a lot of reading (on and off for about a year). I can't give you first hand experience but i'll try my best.
1. It is true, by using hot water, it is better for the cham. They are cold blooded animals and regulate the temperature based on their surroundings. If you spray the chameleon with cold water, it drops its temperature and then it has to bask to warm up again. I assume that it will stress the chameleon. Also, unlike humans, chameleons prefer warm water to drink as opposed to cold. It simulates their natural environment better. Put hot water (not boiling, mind you) in a fine mister and then spray it on your hand, it should be warm but not hot.
2. It would probably be pretty hard to tell as juveniles grow at an amazing rate. (read: i have no clue)
3. You will need a UVB light so that the chameleon can produce vitamin D3. This is ESSENTIAL so that Metabolic Bone Disease won't develop. (you also need to gutload/dust feeders so it can get adequete calcium)
4. From what I read, you can keep your Chameleon inside, but natural sunlight is very beneficial (better than anything you can buy) for D3 production. If you're worried, take him/her outside on a nice day and keep him/her supervised. If it's in a screen cage, keep it elevated, that way rats can't get to it, and bugs shouldn't get in, but you'd have to make the call yourself.
5. I would not keep the lamp closer than 12 inches away, depending on how hot the bulb is, you may have to change it. Also, buy a thermometer!!! ensure that the basking spot is the right temperature and then keep your hand under it and see for yourself how hot it is.
6. you'd be safe between 50-60% i think.
7. House flies are too small, a juvie probably wouldn't go for them. Also, if you're concerned about pesticides in your area, it wouldn't be a good idea to use caught insects. I've read that chameleons really like silkworms (but they have a poor calcium
hosphorous ratio so these should be given sparingly, like a treat) other than that, mealworms, superworms, waxworms, butterworms, roaches, moths, pinky mice (when adults, if they like them). You may also want to try giving them some fruits and vegetable. My friend's female loves tomatoes and strawberries! Cater to the animal's taste.
8. Unless they are gutloaded and dusted, most feeders are essentially empty food. They have no real nutritional value. You are what you eat!
9. I really don't know, sorry. My friend never had that problem but if the chameleon is climbing on the screen, make sure the mesh isn't tight enough to rip off a claw, it won't grow back.
I really hope that this helps. A reminder, I have never personally HAD a chameleon, but I do read a lot about them. I hope to get one myself soon, but it will be a few months before our petstore has any in stock.