You can also alter things a bit if needed, for the bottom of the tree to work itself sideways a little with each round you cut off. By not cutting straight down, rather towards the side a little. If you are looking at the tree saying if I could pull the bottom of it this way some it would fall right down - then do your cuts so it will do that. Looks in pics like there might be a weak branch up there in the crotch holding it up, So if you could work the bottom that way it might take the load off the stronger crotch branch & put it on the weaker one and it might let go & come down.
But you need to be careful of course, as with all things done with this stuff - if you go sideways too much and you're standing in the wrong place it could kick out towards you when it lets go. Dance time then for sure.
Also hard to tell scale of pics in this case and just how big this thing is.
I'm going to cut the small branches that are lodged against the support tree,with a pole saw,that seems like the safest bet.I believe when one is cut the tree will slide down in a hurry,but I'll be back about ten feet ,pictures tomorrow ,I hope.