I'm wondering some things. He sounds quite incapable of getting in a car, driving to a store and buying alcohol. Where's he getting it? Cutting that off would be my first task in that situation.
I don't think he needs alarms. He needs 24 hours of attendants.
"Putting him in a home" is far simpler sounding than reality. There's the cost, accounting if there's subsidies or government money available and he has to "meet criteria" to get into assisted living or higher facilities. There's also the legal part. You can't just take charge as the responsible person taking care of the irresponsible person. You'd need the court to agree and give you power. A POA is not even close to enough as it's set up so you can act when he's unable to, but he can revoke this at any time or over-ride any decision you make. So something like conservatorship which isn't easy.
With all these prelims out of the way, without government intervention, he really can do what he wants. If that's standing in the street in the snow in his bare feet at 3 in the morning, ya, he can do that. With nobody there to suggest he turn around at the door and go back to bed, he probably will do that.
We are providing him booze via delivery. That's his wish, it's been his explicit wish for years. As I stated in my original post, we aren't wondering what to do for him overall; an assisted care facility is a no-go unless 1) we can find no caregivers (it's a very small town, population about 10K); or 2) he asks to go to one (which he never will).
We've already been down the road of having a legally appointed conservatorship (his spouse) to make decisions on his behalf and have him legally institutionalized against his will for treatment (that was about 5 years ago); he was absolutely a danger to himself and others at that time, but as soon as he was sober for a few months he petitioned the court to get his rights back and got them. He's hated his spouse ever since and made her life miserable with blackout drunk dialing and verbal abuse ever since (they have been separated since then).
He's raged against nursing homes etc as an option even back when he was a relatively sober, very successful and high functioning adult in his 50s (he's approaching 80 now). He busted his ass to keep his own aging relatives in their homes with onsite care and fully expects us to do the same for him.
He has been through literally hundreds of thousands of dollars of private rehab at the best facilities in the country, as well as multiple rounds of court-ordered rehab at free facilities. He has been jailed for DWI multiple times and been in forced assisted living for 6 month stretches twice.
He's tried to stop drinking multiple times, and almost died countless times detoxing (both involuntarily and voluntarily).
He was sober for a stretch a couple of years ago and had suicidal ideation even when sober. He's done and he wants to die. To try to continue to support him in terms of overall health is weirdly, a form of abuse at this point. Certainly, putting him in an institution would be a form of abuse. We are trying to go with the least bad 'abuse/misery' to abide by his long stated wishes. We all wish (not in a hostile way) that he would just die already. Not b/c we don't love him (he was actually a fantastic father to me until he had a meltdown when I was about 17), but b/c HE clearly wants to die.
Unfortunately, assisted suicide isn't an option (and he wavers day to day on whether he wants that anyway). Alcohol is all he has at this point and he wants to kill himself with it. We're ok with that, he's ok with it, the caregivers are ok with it (most caregiving agencies will work with active addicts and not interfere with their use).
The problem is when he's less drunk he's much more mobile, but he has damaged cognitive capacity regardless, so he's actually more of a risk to wander when he's more sober (er).
So our problem isn't the booze, ironically. It's when he's not getting enough booze and starts to get more mobile, anxious, and hostile that the trouble starts. He's been drinking wine instead of hard liquor the past few weeks and that's probably why the wandering has popped up.
Hence the specific nature of the question about how to monitor him when he wanders.
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Great responses in this thread. A lot to digest. I knew I could count on you guys here, thank you!