1) I wouldn't keep them together unless it's a female/female or male/male pair. Even then I would be carefully about housing them together.
3) Silkworms, Phoenix worms, crickets, leafy greens, mice pinks (if you can find some small enough for your hatchling) and the occasional boiled egg bits is what I try to feed.
I stopped feeding mealworms quite a while ago. Silkworms are softer and easier to eat, and have a much larger variety of sizes. Phoenix worms have an amazing calcium level, and have that softer-body-and-no-biting plus side as well.
Both can be found at http://www.mulberryfarms.com
I honestly never liked mealworms for as long as I fed them :/
Right now my own Savannah is on a strike and eating only Silkworms. Every time I offer her anything but she gives me a look like I'm nuts. Still, it's fun to watch her eat. She's just over hatchling size and likes to do the head shake when she chows on her silkworms.
Cutest thing ever
Savannahs are pretty much my number one favorite lizard of all time xD