I'd try it. I don't know if those are safe. One trick is to make sure the wood is completely dry (so it won't rot inside) and then spray with a couple coats of polyurethane. It will hold in anything toxic, repel water, be cleanable, and still retain most of the natural texture.
it doesn't. I've done it for years any time I wasn't certain if a species of wood was toxic. especially with geckos, who may be inclined to lick drops off a branch after misting.
for species like maple or manzanita that I know are safe, I don't use poly. I also don't bake the branches, it generally just makes them brittle.
I'd be worried that the poly would make it to slick for a animal to be able to climb.