nzkiwiman:
Any offer they made will need to be in writing and be able to be presented to a employment lawyer (the community law centre, I don't want to spend money on a real one). Until then, the resignation is still active and the timer is ticking over.
One of my friends has made a suggestion that I need to lock in any promises that they make into my employment contract with penalties if they break them (and probably if I break them as well)
Just to be clear, I would accept their offer and take their money and complete my work as I'm paid to, but I would probably just accept that it's time to start looking for something else.
Remember, you wouldn't be in this boat if they valued you in the first place and they've already shown they are happy to take things to the limit of what is reasonable and possibly beyond in terms of what is legal. You can spend time trying to engineer a contract you don't think they can breach, but they'll just ignore it and play percentages if they really want to.