G'day frdnicholas,
To my eye pruning and seaweed are needed.
Cut off all the branches that are growing less than two foot above the ground. Then prune the rest of the tree to a vase shape. This means chose the four most healthy-looking branches spread evenly around the tree and cut off the rest including the central ones. This gives you the open vase shape that most trees are pruned to. You can then trim the four main branches back to a length that looks structurally sound. Drastic I know but this is the way with unpruned fruit trees.
Give a seaweed (high potash) spray to all the leaves and around the dripline. Weed around the dripline first, remembering these are shallow rooted trees. Mulch.