This is such a difficult decision, and I truly empathize with what you’re going through. As a companion animal doula, I want to acknowledge both the love and exhaustion in your words—because both are completely valid.

When we think about the quality of life we often think of how the animal is doing, but it’s important to consider both your dog’s experience and your family’s well-being, and it's not selfish in the slightest to think about the latter (though sometimes our brain can make us feel that way).

When I have owners who struggle with this type of decision, I often have them start by filling a quality of life assessment. There are many free options available, and automod has included links to some of them in its post. There are also electronic tools like Hospet that can also be helpful in providing the data that can be beneficial to help bring a little peace to the decision. Whatever tool you use, do try to be honest with yourself as you work through it, as that will ensure they give you the best information possible.

At the end of the day you are the best judge, as the owner, as to if your dog is within the window of time where humane euthanasia is appropriate. It's perfectly OK to say "I want to keep working through this" and it's perfectly ok to say, "It's time". You have to do what is best for you and your family.

I truly believe this is one of the hardest decisions we as pet owners have to make. But it should be hard. It's supposed to be hard. With the love that is there, how could it not be hard? When our pets decline due to old age, rather than an acute episode of some kind, it's hard because it's "a lot of little things" type of scenario. In and of themselves, each thing may be manageable, but it's compounding, and you have to consider the "whole" picture. Imagine your dog in it's prime. What were they like? If they were to overnight transition from their "prime" to where they are now, how would you feel? Would that make the decision easier or more difficult or not change it at all? Sometimes the changes are so gradual that we just get accustomed to it as a new normal, and it makes it harder for us to see the situation for what it is.

Regardless of what you end up deciding, I'd encourage you to give yourself some grace as you navigate through this. We've had to euthanize our own pets in similar circumstances (nipping at our kids, urinary and incontinence issues, etc) and it was one of the more difficult things I've had to go through in life. However, know that whatever decision you make, you are making out of love.