For what it's worth there is a vital concept we have to remember about our ownership of animals. From our side of the relationship it's quantity that matters (we want them to be here forever!) but that quantity is no good without quality to go with it. From their side it is the quality that matters most, 6 good years are better than 16 poor ones as I'm pretty confident that animals don't have a well developed concept of "future" If the now is miserable for them then it's no good.
I also firmly believe that anxiety is as bad for animals to suffer as pain. I have seen countless patients who suffer chronic anxiety and lets be honest, being stressed and anxious is thoroughly unpleasant.
It is very hard to assess the effect that degenerating senses has on animals for obvious reasons but signs of dementia can be very varied.
Generally speaking I have seen little success managing dementia signs but I tend to start with a pain relief trial and if I see no response to that then one can try other medications such as anxiolytics and circulation boosting medications but results are variable.
Sometimes the only way we can stop our animals having a poor quality of life is to let them go, as painful as that is. The other factor is often human (child safety) if kids are old enough to understand to leave them alone then that can be managed but if they are young there is always a risk and it does make it a difficult situation.
Have a chat with your vet about any recommendations they may have, but I would always say never lose sight of the concept that letting them go is always going to be too early for us but it is better that, than letting it go on too late for them. Bloody sucks and you have my sympathy.