Stopping Dry Rot in Living Fruit Tree

We topped a couple 3 inch branches many years ago on our now 30 year old Santa Rosa plum. I saw some white on the bark and stuck a screwdriver into soft wood. I cut some more off this branch and it had dry rot (white). I kept cutting and am now to the trunk and the dry rot continues. I dug out what I could.

Can I:
1) Use an antifungal paint (like I have used on the edges of my new roof (powerful, green, and oily) or antifreeze (glycol) which is water soluble or some borate to kill the dry rot? I wouldn't put any of this on the cambium. Any other suggestions to kill the last remaining dry rot?
2) Then fill the hole with blown in foam, smooth it off and paint to seal out pests, more dry rot spores and water. My main cut is now vertical.
3) No we don't want to remove and replace this tree.
Peace.

By James D.