1)I never breed a female panther chameleon until its over one year of age and full grown. I do this because I want to make sure that she is finished growing her own bones before I put further demands on her calcium levels to produce eggs. She might produce infertile eggs before that, but that doesn't seem to cause any problems.
IMHO since breeding a male doesn't affect his calcium levels, it would be okay if he were younger...however, I have no idea if his sperm would be "mature" enough.
2)Whether or not you need an incubator depends on the temperature in the area of your house where you intend to incubate the eggs.
3.)Sorry, can't tell you how nutritious lobster roaches are. I can't find any comparisons on them. Providing a variety of insects as food for your chameleon is always good though.