I got my PhD ten years ago. Yes, it was a slog; yes I had no money; yes, I fell out with my supervisor and yes I nearly gave up (several times). It was worth it. I now have a fantastic job - I could never have dreamed of this before - and there is no way that I can regret any of it.
Jenni - have you considered that your 'long dark night of the soul' comes from your longing to do well and the depth of analysis that tells you what needs to be done. Take it as a sign that this is how it has to be - sometimes. Hang in there, this too will pass.