I'm sure some FISOs will respond. In the meantime...
Depends on how much you need to live. FISOs are paid, but not a fortune.
I do not know about pay arrangements during training.
In response to your last, yes - that's about it... and watch the adverts.
Presumably you are fully familiar with this:
http://www.caa.co.uk/docs/33/CAP427.PDF