I'm not thrilled with any of the earlier answers because no one addressed the apparent decay. Of the wood I can see in your pics, all of it is rotten and that's why it went down. The rot probably goes up the tree beyond the top of the highest scars visible on the bark. Wedges won't work in weak, decayed wood, so you have a complication there.
I suggest you cut into the tree here & there to see how far the decay goes, then you would have a better idea of what you are dealing with. And note that at some point along the tree, the decay may only be near the center of the tree, so you won't know for sure where the decay ends until you cut all the way thru which you don't want to do while you are just checking the tree.
I would guess that the safest place to cut all the way thru is near the limbs because they support one end of the tree. The lower end of the tree will probably not roll as the butt end will is stabilized by the fork in the remaining tree. The portion with the limbs may roll one way or the other, but it won't come downward on you--it may go upward. If the wood is sound where the limbs start, begin your cutting from the top of the log and use wedges as you go. As you get part way thru, stand back and hold the saw at arms length or as far out as you are comfortable so you will have a little space between you and the tree in case the unexpected happens.
With the top cut off you may be able to pull the lower part loose with your tractor.
Good luck on this and let us know how it goes.