Definately ratchet strap it like some of these other guys have mentioned. Is there another tree nearby that you can tie in to?
Did a nasty poplar late fall that had a bad lean to it in soft ground. It had started to pull out of the ground a little. I tied into the other poplar right behind it as a precaution and everything went really well.
Just remember, as soon as you start dropping weight out of the tree, you are USUALLY taking some of the pressure off of it that may cause it to fail.
If this tree has you stressing that much, maybe you should just walk away from it? Especially if there isn't enough money on it. What's it really worth to you?
How long have you been climbing?