Oh tree's. I totally understand where you are coming from. I am so hard pressed to ever cut s tree down for any reason. I had one of the pine trees get hit by lightning and tried so hard to make it okay, but it wasn't. I knew that thing might fall on my house so I agreed to let them cut it down. I was so upset, all I could think about were the birds that would nest there. My son, bless his heart, went up on a ladder and moved the nest. I thought it the sweetest gesture.
If the tree is infested and beyond help it needs to come out. Cut the loss take it down and plant a ne one. remember to treat the soil if it is a fungal problem. It is painful I know, but you will have a new stronger tree instead.