First let me say you are a great Sister to have, no one in my family would help when I had a similar situation. Sometimes being out side the picture you can see the over-all much more clearly! A large dog eight years old is getting up in age and with med problems may even be a shorter life exspectency, it will demand more attention, and cause extra stress on your life, especially your work, My dog did and I found myself taking more time off work and my boss was giving me that look! It is difficult to look at your beloved dog and say it is not a human being, but it is not, if it were then God comes into the picture and life is at a different level, if you understand where I am comimg from? We were actually having financial problems because of the dog, but once it was behind us we got out of debt almost immediately! I had my vet come out to my house and it was the most tearfull experience in my life, I buried my best friend on this planet on our property and planted flowers in a heart shape in the spot and he will be remember until I die! Hope this helps but some times you have to stand up to the plate of life, make the best decision, and move on!