First - I have heard that that Nature's Miracle is great stuff. It gets rid of the enzymes that cause the odor. Or ask your vet what they use.

Second - I think that the plastic tubing for the wires is a great idea! THEN spray them with bitter apple (cats also hate the smell of vinegar - my mom used a small patch of cloth soaked with it to train her cat away from dragging all her pencils, etc, out of a pencil holder).

That poor cat from next door - maybe try to find a low cost spay-neuter place. And maybe animal services should know about this?

Would some neighbours chip in on the neutering?

Good luck! Don't give up - something will work out.