Hi Beth,
Your description of poisons in manure sounds bad and I can’t believe anybody wants to rid their land of clover.
So it is a good question about woodchips. There is a grower in Britain, Iain Tolhurst at http://www.tolhurstorganic.co.uk who makes potting compost from wood chips, but he turns the pile regularly with a digger for several months. You don’t have a digger but giving the chips longer to rot down will see them turn to something more compost-like and suitable for gardening.
Tolly says there are just a few trees to avoid (I am unsure which ones) but most chips work well, so good luck. Green, fresh chips decompose much better than older, kiln-dried chips which are sometimes used as horse bedding – I have discovered this the hard way, they endure for a long time.