You don't need to tell where, and you can use a one-off generated password that you really didn't memorize.

A) The idea is that the "rubber hose collection" leads to you revealing where it is, and B) if it's a generated password, how will you stop the deadman's switch in the event of getting away?

You ping the service by email/phone/SMS, not by logging in. But you have a point, you'd have to keep pinging it for the rest of your life and it would fire anyway when you die :)

Not necessarily.

You could say, I have a bunch of documents that implicate you and they'll be sent out to authorities should I not answer my email or phone at N time.

"I know you really don't want to tell me where those documents are, but maybe you'll tell my friend, Mr. Hosey?"

Maybe, but this is the case for any dead man's switch (even a bank/lawyer). It's always a balance between what the mob boss thinks he can get you to do vs the power of the dirt you have on him. Literature/TV have beaten to death the permutations/twists on this theme.