Hi Angie
Don't try to get him where he doesn't want to go, unless you want the fight! And, really, do you? What is going to be lost from him sleeping where he wants to fall, apart from offending the social mores; and what is going to be gained from you busting your soul, in the most of your loving gestures, to maintain the norm, to get to a place which you consider is normal? Nothing; you have to work this on its own terms, all of which will throw your best and kindest of intentions well to the winds.
Is he comfortable, warm and safe where he sleeps? Are you comfortable with where he chooses to rest such that you are at rest yourself? Can you manage all of that together? Stairs are frightening for an AD sufferer - what you see is a precipice to hubby. So, and it is only a suggestion that worked for me for a while, if you have any fairy lights left over from last Xmas or go any buy some, lay them down the very inside of your stairs, inside of each stair, so that they don't look like a black hole in which he might think is danger!!! Just a thought. Trial and error.
Chesca