So for now I haven't been able to figure out robbery-safe vault setup
There is not one. Any set up which you can access yourself, you can be forced to access by an attacker if the consequences for not doing so are great enough, either to yourself or to your family. Even in the timelocked set up you describe where it is utterly impossible for you to access the coins sooner, there is no way for you to prove that to an attacker in order to get them to stop their attacks, and as Loyce says, they can just kidnap you and wait. They can force you to access any back up, unlock any wallet, log in to any account, or contact any third party with a gun to your head.The best way to protect your funds from robbery is to have no evidence that they exist, and to be able to hand over something to an attacker in order to satisfy them. This means at least one wallet which no one knows about, created in a completely airgapped manner, with no evidence left behind, stored completely separately to your other wallets (including its back ups). It also means this wallet is funded only with coins which have no link to your other coins. You can't just empty 5 BTC out of your hot wallet and send it straight to this cold wallet, since it will be clearly obvious from looking at the blockchain what you have done. It needs to be funded with well mixed or coinjoined coins, preferable bought peer-to-peer and not via a centralized exchange. You also need to have other wallets you can hand over to an attacker. You might already have a hot wallet on your phone you can hand over, but the attacker will still expect that you have a cold wallet too. So you need a decoy cold wallet or two with an amount which could reasonable be "your stash" which you could also hand over in such an event, while your real cold wallet(s) remain hidden.
Extremely helpful, especially in terms of clarifying what has now become so obvious to me but previously not understood - that every set up I can access, I can be forced to access by an attacker.
Thanks a lot, o_e_l_e_o!