That crack is 1 1/2" wide. Bash a Bong into it on an angle. If that does not work cut it off with a hacksaw. The crack is shallow. If the rope is too short put a sling on it. Just pray that a branch or the whole tree does not fall on you while you are on the rope underneath it. Whose property is the dead tree on?
The Mohonk Mountain House and the Mohonk Preserve have done a great job protecting the environment thus far, but ... it's all down hill from here http://youtu.be/9AU8fMo8v4k.