The only thing that materially differs from my analysis is that you're using Core to set up a multisig wallet. But all my other points stand. It's still two general-purpose laptops. All 7 keys are generated by the same binary on the same machine, and signing happens on that same machine, so the multisig doesn't remove the single point of trust you warned about. Such a model still has many weaknesses, and is still a poor fit as an end-user product.
The bottom line is Bitcoin Core as a software project was NOT started or designed as a Bitcoin wallet. To the extent that a wallet was included, it was a dumb accident. Using something for a task it wasn't primarily built for, and that doesn't get the same amount of care or attention, is just insane to me.