All, thank you for the input.

No, I do not have a scope base installed any longer. I have an F Class scope base that extends over the nut, and I was compelled to remove it to get the wrench on.
Yes, I believe my understanding of how the receiver and recoil lug were attached was fundamentally flawed. Closer inspection of my pictures shows there is no keyway for a lug to fit in. I should be able to spin the action and recoil lug off, with a bit more oomph, but since I was sure there was a keyway before, I didn't attempt it. I'll try this tomorrow.

Thank you everyone with your experienced inputs.