EP - hang in there and dont quit, you have put too much into the training to jack it all in now.
For what its worth my swimming is still rubbish and I am fearing not even finishing that part, cycling just getting over 14mph now on 60m plus rides a little bit hillier than Outlaw and run (well walk) after my own HIM at weekend just gets me inside a 6hour marathon.
But I have trained bloody hard just like you and I will be at the start and see what I can come up with on the day, just like you will.