Doc,
Well yes, this was very much a learn-as-you-go type of project; in future projects I will certainly do things differently.
In the meantime, I ordered a relatively cheap ferrule crimper and a bunch of ferrules. Perhaps not ideal given the screw terminals, but no doubt better than what I have now. I'll look into immobilizing the wires. I'm using a 3-wire, 22 AWG cable.