Originally Posted by
lillamy 
Just be aware that the shift in your behavior when you start planning may set him off even more, even if you don't think you're changing. That's what I saw happening - I had to leave much earlier than planned and with much less preparation.
Lillamy makes an important, important point. Raging control freaks KNOW when something is different. They are in tune with any changes in your personality because that's how they control you - by reading you and taking their control freak steps to nip that in the bud before they lose that control over you.
Don't let him see it in you. It's hard to act as usual if you are planning to leave, but it's important if you are fearful of his reaction.