"does it actually say in writing anywhere that you cannot be discharged for failing your fitness test? only your attitude towards it?
What would happen if your attitude to fitness was 100% but was still failing the test?"
It doesn't actually say that you can't be discharged for failing your test (it doesn't need to). What it does say is that you can be discharged for poor attitude towards fitness, and that personnel with a good attitude towards fitness should not be penalised for failing.
In theory, if you have a good attitude to fitness, and exercise regularly it would be unlikely that you would fail the test, BUT the system does allow for discretion at the various points of the procedure. For instance, the Flt Cdr my see that Bloggs has improved his run score on his third failure, and even though it is still a fail may not take the appropriate third-fail action at that time, as he (Bloggs) would appear to be making an effort to pass the test (and therefore showing good attitude to it).
Eighteen months is the theoretical minimum time it could take. In reality, because of the above, plus probably some reluctance by LMs to take action, it will take much longer ("We'll just give him one more chance"!!).
MM