You don’t need to do any more diagnostics.
A tip... I think when you call the vets, don’t just describe symptoms, tell them what you want to do, that you think it’s time. As long as you call them with a problem to solve, they’ll try to solve it thinking that’s what you want. Don’t wait for them to suggest putting her to sleep, because they’re very reluctant to do that as long as an owner wants to try, they’re trying to make the people happy, and owners who aren’t ready don’t react well to a vet wanting to kill their pet.
Thanks. The Mrs. has just been wanting to ask them if they think Abby is in pain. But there’s no way they can know that, especially without seeing her.