If there is a commercial orchard nearby take a look at how open the trees are- you will see that there are not more than 4 major branches coming off any 4' of trunk and an open center tree needs no more than 4 main branches altogether (I generally prefer only 3).

What you need is a lot of thinning cuts of entire branches right to the trunk to begin with until the tree is reasonably open- a point that is difficult to explain, but the old timers used to say you haven't pruned an apple tree enough until you can throw a cat through it.

Don't get to this point only by removing branches where they are attached to the trunk but also remove secondary and tertiary branches that crowd each other. How much and which smaller wood you leave on your main wood should be determined by each scaffold having about equal access to light and equal territory without any overlapping wood from competing scaffolds.

The greater the diameter of the scaffold or secondary branch the more secondary and/or tertiary wood should be left connected to it.

You won't kill this tree by removing too much wood.