If I were going to use jumping as method, then :
I would want to find somewhere that is 300 feet ( 20 floors ) or higher.
Also I would want to be certain I will fall without interruption or landing half way down on a ledge or something.
Plus I would want to make sure I hit something hard, and that nothing could break my fall.
Ideally I would also avoid windy days if possible since that could interfere.
54 floors would be fine, but also pay attention to all of the points above.
Note : As always, please note that I strongly encourage you to seek help with whatever is troubling you. Things may seem hard, but with the right help they can improve. There are many sources of help if you look and reach out. Please seek assistance in any and every way possible. You alone must decide upon your actions and take full responsibility for them, and you should always favour seeking help and keeping out of harm's way.
As long as you hit something solid and don't land in a tree, bush, soft soil, or water. High winds have been known to save people too so I'd avoid a really windy day. I think your chance of survival would be very low despite any of those variables but still wouldn't take any extra chances on it.
Just make sure you don't have any reservations about it if it's what you decide. I'd imagine it to be scary standing on the precipice like that.
I copied the "windy" part of my reply from you, b.t.w. Credit where due.....