Some of the Forestry organisations have been waging war on rhodies, have a google and see what you can come up with.
It's incredibly invasive and incredibly robust, I'm afraid.
As a firewood, it's a lovely hard wood, so will burn if well-seasoned, yes.
On the poisoning livestock front, I think it must be mostly a problem to livestock who aren't used to it. The stuff is all over Exmoor and so are deer, Exmoor ponies, and a lot of sheep, not to mention some wild boar. Presumeably the indigenous animals learn to avoid it, and/or their systems adapt to it.
We have yew overhanging one of our fields, and the sheep nibble the ends of the branches. So far as I know, none of them has been poisoned - although we do sometimes get bought-in sheep falling ill for a while when they go into that field...
