Thanks for replying Lateralus. I really am in a no win situation given how much I know what this means to him. I'll take your advice and balance it out with what others here will hopefully add to yours.
Really sorry about dropping this in at a time like this for you and your dog.
I didn't read your post until after I posted mine.
This may sound a bit cold and to the point, but as an Antipodean I'm sure you'll appreciate my honesty.
Putting your dog down will be the kindest thing to do (as I'm sure you'll already realise) and even though it's obviously upsetting, it's best to try and remember the better times.
This is going to sound even colder, but I wish I had the option with regards to my father given the state he's in at the moment. :/