awesome questions!
in order:
a lightweight enchantment can be put on a wand, but it might take another wand to do it.
bones and wood make good conductors of White Magic because they contain traces of life. Wands aren't often mass-produced, as most people will only need one in their whole life.
a 'wand' is just anything you use to channel magic through. you can make anything into a wand, though larger things will require larger pieces of soul and may effect your health. one of my characters actually just has a five-shot revolver as a wand.
the limits of magic are essentially your ability to perform it. elves, for example, are stronger in White Magic and don't often need a wand, while humans aren't very strong in any form of magic and so will need a wand even for more basic spells. magic can rarely stretch beyond it's users surroundings, like you couldn't cast a spell to eliminate half of all life in the universe, but you could, with exertion, end all life within about ten feet of yourself.
wands aren't exactly limited to certain materials, it's just better or worse outcome. think of a wand as a multiplier; a human doing magic on his own has White Magical ability X times 1, but when he has a wooden wand, it becomes X times 3, while with a stone wand, maybe X times 2 or X times 1.5. a metal wand will probably be X times 1.5 or less White Magic effect. see? and turning a still-living thing into a wand would most likely kill it, with having two souls inside. but one character I wrote up had actually turned himself into a wand, it didn't work out too great, but he survived and had amplified his power extremely.
there isn't exactly magic medicine, but potions don't require magic to brew, and can have often the same effects as spells.
when I said 'wood and bones', I meant really just any organic material, nails, teeth, hair, plant stems, and there isn't really a process to making them, it's mostly just a magic instinct thing.
and for the last questions, any organic material works. yes they do. it will still work best with White magic. No, you can turn literally anything into a wand. if trees are sentient, no one has found a way to communicate with them. Where there are races there is racism. This world is more of a blend of modern technology and medieval technology, because magic is part of science.