They would only find decoys unless they knew exactly how many layers deep the cold storage bitcoins are buried. Then they need to know how deep the n factor authentication is buried. Then they need to know what countries and have the authority to find where the multisignature and SSS keys are hidden. Your street thug will need "a particular set of skills" to pull that off.
Do you not read the part about "kidnap and torture"?We're not talking about hackers here(and even they use social engineering to do so if they could).
No ,they only need to know who the person who that holds that bitcoin and torture them to hand their key. If they couldn't/refuse to cooperate ,well too bad ,you're dead.S/he need not be a technical expert to do this , the depravity and willingness to inflict pain and fear are the only "a particular set of skills" necessary.The simplest way break a unbreakable safe is always to get it from someone who knows the key.
No, you don't understand Bitcoin at all. Sure they can kill you, so what? They get nothing. And guess what, there are also ways to hide the information necessary for heirs to receive the bitcoins in the event of your death at a future date. I won't even get into the ways bitcoins can be used for anonymous vigilantism in the event of a death by foul play.