My impression of the herb/spice distinction is that herbs are generally the green parts of a plant, while spices are generally seeds, berries, and other parts. For example, coriander is a spice and cilantro is an herb, even though the former is the seed of the latter.
You're probably right.
I think so too; though older english useage appears to have been to refer to edible green plants in general as herbs, at least that seems to be what the King James version of ChristianBibleGenesis/One 11-12 is referring to...
Common herb mixtures: