Well you shouldnt leave anything with anybody (and I'm not sure what the red book is youre talking about - maybe that's just one of those uni id things and doesnt really have anything to do with this.) as far as i know and in my experience with my current and previous positions, all you need is the visa and the res card, and a valid res card alone will be sufficient to keep you legal as long as you are still with the school that supplied it.

as i said before, if you get a new job, your new employers are obliged to organise a new res card and visa for you, and you would be holding onto your other ones until they did so (well your visa's in your passport anyway and you are the only person who should be holding onto that!).

of course you can't blame them for testing the waters with you about extra work - if you did take it it would save them the problem of looking further for a teacher, and another person in your place might have wanted it anyway, so i don't see there's too much to be concerned about there.

as far as taking 14 classes a week, thats a pretty standard load for a foreign teacher - not heavy by any means, and obviously because you are inexperienced and they have employed you they cannot expect any more from you than what you are able to provide - and this will get better as you find your way. Teaching writing is my favourite anyway - you dont have to be too focussed on organising speaking activities for big classes and difficult to accommodate students. I think you're doing ok. email me if u'd like a few suggestions for your classes.

good luck!