Thanks for the explanation D. I thought it may to come down to that.
Thinking back on disabling the interlocks, was that even necessary to bump start? Or did that just enable the starter to operate under any condition?
The latter, I should think, flash!
With the ignition ON, and with the safety switches either in the GO condition or bypassed (as you've done), the success of a bump start depends upon its vigor, relative to the battery condition (IMHO).
Just for kicks; with ignition switch ON, roll 'er down a hill, in maybe 3d gear; pop the clutch and see what happens!