Lenore I have my own very firm views on what I would be prepared to live with. They are my views for myself, not others
I'm just kind of saying that this disease does not follow particular predictable paths, and falls can happen suddenly when walking seems not too bad. I know, my husband had many falls, and two of them caused serious injuries that impacted on his quality of life. Every time he fell he was not doing anything radical, he would just be upright one moment and hitting the ground hard the next. I will say he refused to use walking aids as much as possible and every fall happened without any aid. OK I just remembered one fall happened when he got really angry he couldn't blow his nose and threw the tissue at the bin and missed, so he decided to kick the bin ... lifting one leg was not smart at all, and fortunately even though he hit the stove with his head on the way down that particular fall did not cause injuries, just more fury
I also believe in acceptance and in letting PALS make their own decisions then standing by them and advocating for them.
It could be very worthwhile checking out thoroughly the palliative care services you have in your area now. Find out what the differences are between them and who you would maybe work with. A good palliative team will support his wishes and give you both enormous support. You don't have to start with them now, but things can change suddenly with ALS, and there is nothing worse than trying to make decisions in crisis.
Have you done all the legal documents? Living will, power of attorney both financial and medical? Get them done now, again, don't get caught in crisis.
If you can make some of those decisions and put things in place, you are both more likely to then start to just live what you have now, knowing you are prepared (as much as you can be).