I was successful in using #nostr #safebox for this transaction.
I deposited the funds using one machine (my MacBook) and using the recovery phrase, sent the funds by accessing the safebox on an entirely different machine (a vps). Not only impossible to trace the fund flow, it was impossible to attribute the transaction initiation from any one device.
The proof of concept for #nostr #safebox is now largely complete. I am spending the next few months shoring everything up for an initial software release.