Update:
Thanks for all of the suggestions. It sounds like there are as many questions as answers. So, to provide more information.
Tools I have at hand:
Chainsaw
50 feet of 3/8 grade 70 chain
LS XR4145HC tractor
3 ton Wyeth Scott More Power puller with 20' synthetic rope
A ladder
More pictures (see below).
The end is only hung up on a small tree (see images).
I don't like the idea of trying to take the main tree down at the same time as the hang up. Who knows which way the tree would fall/spin/etc. I also don't want to try to take the hang up down by felling another tree to hit it. If I were a professional and paid by how quickly I would work, those might be quickest/easiest, but a pro I am not. I'd rather maximize safety at the expense of time.
My thoughts are as follows.
Throw a rope with a wrench over the hinged end, and then put one 25' length of chain around it. Put the other 25 ' of chain on the drawbar of the tractor, and span the two chains with the more power puller. Using the more power puller, pull on it at 90 degrees to the hung up limb (out of the page relative to the first image that was originally uploaded). This should keep me about 30' away from the hung up limb.
The handle on the more power puller will bend before I risk anything blowing apart and slinging pieces at me. If that doesn't pull it down, invest in a pole saw, repeat the same process, but now stand on the far side of the hinged limb (still pulling into the page) and cut a little of the hinge from the ground (pull on it) cut a little more (pull on it) and repeat.
Pictures are as follows (1) view from behind the hinge, (2) view from front of the hinge (I would be pulling out of the page in this image). (3) view from the hinge looking towards the end that is hung up. (4) view from the end of the hung up limb, showing how the notched end is hung up on a smaller tree.