Hang in there Flo,
I know exactly how you feel. I was the same. It took me 5 years, so I know the feeling of seeing what I thought of as the 'new' people write up, submit and pass. Like you I thought "I can't quit, otherwise all this time and anguish will have been for nothing." Just keep chipping away at it, and eventually you will reach a point where you suddenly think "there's not much more to do!". All theses have 'holes' and that's the truth. The good thing is that your examiners know this too. There's a great article called something like a 'It's a PhD, not a nobel prize' and I found this a useful mantra and a reassuring read.

Try and reach a compromise. At my university the success rate of those that submitted without the support of their supervisors was not good. Having said that, I reached a total communications breakdown with my supervisory team some months before submitting so it was not so much without their support as without their knowledge. Instead of carrying out more work can you just add recommendations and acknowledge that further work might yield new questions/outcomes? Maybe just tying up the loose ends with a few carefully crafted caveats? In my opinion, this is essential to reach the end, otherwise more loose ends just keep appearing the longer you work at eliminating them.

I finished my PhD last year and had a very tough time getting to the end. Unfortunately I have not been able to find ANY kind of job since being awarded my doctorate. I started a landscape gardening business to get me through financially when my funding ran out and this is just about keeping me afloat at the moment but is not what I want to be doing. At the moment my PhD feels like a massive waste of time effort and money. There seem to be very few post-doc opportunities (on this site there is not a single earth sciences post doc listed) I want to be an academic and a PhD is essential for this, but equally it's useless when there are no jobs and bills to pay. I now find myself in the 'over qualified' bracket- a term I have always hated- for many jobs, or alternatively lacking experience for commercial sector jobs.
Grrrrrrrr