Okay, but even if all that you have said would work, I don't know that it would work fast enough, because I know that the complex that I live in would dispose of my belongings within a week of my death, so that the apartment could be re-let to someone else. The items would end up either being scavenged by the complex staff, with what they didn't take, being set out for other tenants to claim, and everything unclaimed or taken ending up in the dumpster.
Put it between your toes.. haha.Tattoo... ugh!
In real life, I do know someone who keeps a password between his toes.
I don't know if you are asking for suggestions or you just want to have an endless discussion. The only realistic option is thru lawyers. Don't worry if they take your belongings themselves. You won't have time to worry about it by then. Your goal is to get that password to the right person at the right time. This is not a Mission Impossible movie, This is real life. Call your lawyers. Tell them to get everything they want later as long as they do what you pay them to do. End of discussion. Unless you want to start talking McGyver stuff next because I have a good one. In real life, I do know someone who keeps a password between his toes.