You have a very interesting old tree there. Looks like it is quite old or at least so sprawling that you need limb supports for some of the larger branches. At this point you may or many not have some of the known canker causing fungi attaching that tree. In most cases for the several we know about in the PNW the management tactics are similar. Being in the Bend area you already have an arid environment so that is to your advantage.

The main management tactic for these problems is pruning.There are no chemicals or things to apply that will make the infections go away. Removing the tissue will also reduce the disease pressure for the healthy parts of the tree.

That said I am not sure how to guide you on this tree. A large sprawling tree might be its attraction. These canker problems will make branches more susceptible to breakage when you get something like a snow event. Rare but possible. If branches are over structures then if would be wise to prune them back.

I might suggest you get a trained arborist to have a look at it and give you some recommendations. There might be 2 or 3 in the area you can get bids from.

As for information, have a look here at two of the more common problems we find in Oregon:

https://pnwhandbooks.org/plantdisease/host-disease/apple-malus-spp-perennial-canker-bulls-eye-rot

https://pnwhandbooks.org/plantdisease/host-disease/apple-malus-spp-anthracnose-bulls-eye-rot