Might be worth it, if you can manage it on your own terms and to get out of the place with as unburnt a bridge as possible. You've said that you really like your manager as a person, which is probably worth considering; you DON'T need the cash right now, so the only way to look at it is as a favor.

That, or you could think of some thinamabubby you've had your eye on. Is there anything that would cost one week's freelancing salary? Think of that thing, ask yourself if you want it bad enough to do this, and let that be your answer.