How would i add a animation for death on this script?

I'm pretty sure you cannot, unless you hack the Health scripts to mimic some internal health scheme without actually damaging your character.

The reason for that is the Character model has its Joints broken when the Character dies, so any animation would likely just fall apart.

What you're trying to do is deceptively simple, and I would focus on making actual gameplay mechanics before trying to make accessory animations and whatnot. It's easier to code gameplay because you don't have to deal with ROBLOX shenanigans most of the time, and you'll be better equipped to deal with ROBLOX's shenanigans when you already know how to scan a script to figure out how to add something to it.