Nonetheless, I am still waiting for someone to build something that is self-custodial that is dead simple UX that I can give to my 60 year old dad.
I really don't see it happening man, and I say that as someone with a similarly aged old man. It's one thing for us, and even for our kids who will grow up with this technology, but—and I do give kudos to the exceptions to this rule—most of the older generation just won't have the mindset for self-custody. It's too much responsibility, too much risk and no reset button for screwing up (like life, but I digress).
I think this just has to be a case where the custodian has to be a trusted family member—in this case, you, the guy's son.
Now, in the future, when we or our kids are the old people, it'll be a different story. Everything's easy when you grow up with it.