Ok first, at the end of the R key part you should set boolean isdead to false again so you do not spawn all the time .
(Ignore this if you already aee able to kill your player)Then if you want to destroy the player you should use get player character node and connect it to your destroy actor node . But in this case your player is going to respawn and die at the same time so you will not notice it. To notice it you should add a delay node before the destroy actor node. (Ignore until this point)
Nevertheless, if you want for example to have a result like you first press R you die then you press again R you spawn and so on, you should use flipflop node.
Feel free to ask further explanation.
Good luck!