Did you want to sell whatever replacement battery cable you made? I have plenty of suitable wire, but no ends to speak of. The drive to your house is much more fun than the drive to somewhere in Saginaw or Keller that would have ends.
In my experience the PTU has been the overwhelming majority when it comes to causes *if* the tach drops to 0 before it dies. But yeah, not always, as anything goes. It's just so quick and simple to test that as soon as I hear mention of the tach, there's really no reason not to test it first. And being a Nissan guy, I know they fail.