OMG, I am so sorry you are dealing w/ this. Sounds like it has progressed as any typical addiction progresses and has eventually led to illegal pornography (I believe animal porn is illegal) and affecting every aspect of his life (relationships, sex, work, money, sleep). Do a lot of research so you understand everything properly. Go talk to someone who understands addiction and ask for advice. If it is this bad, I guarantee your kids have seen stuff but just not told you.
PS - I would not take advice regarding this serious issue from people on YA. This is a 'real' addiction and requires professional advice. Many women come on here and say their man has a porn addiction when they don't, just because they watch it too often, but this actually sounds like a porn addiction