How can I safely remove a large fallen tree?
I would get some heavy duty pipe jacks to support the trunk, placing them on a square piece of 1" plywood to distribute the weight. Prop the tree with 4x4 lumber to prevent rolling; one end in a hole in the turf, the other end nailed to the tree. Once stabilized, cut all extraneous non-supporting branches, limbs and roots including the portion that hangs over the fence.

Then use a trolley jack to lower the (cut off) tree top to the ground and re-stabilize with 4x4s; carefully chop up the bugger.

It may end up being easier to chop up if you don't let it rest on the ground but instead, land it on some wood cribbing.