First of all, these verses are not meant to be taken literally for the simple reason that self mutilation is a sin. Suicide is a grave matter and can be a mortal sin. Also, the Catholic Church doesn’t accept the theory that everyone who commits suicide must be (in some way) insane and therefore is incapable of full knowledge and cannot commit mortal sin, so that excuse ain’t gonna fly.
Three things are necessary to make a sin mortal: The action must be gravely sinful (this is called “matter”), the person must know it is gravely sinful (this is called “advertance”), and the person must decide freely to do it anyway (this is called “consent”). In the case you describe, and in many (possibly most) suicides, the matter is there (suicide is indeed gravely sinful), the advertance may or may not be there, and the depression and psychological pain may diminish the consent. Because we humans have no way of knowing how freely the person consented and even whether he knew the act was gravely sinful, we cannot determine whether the soul of the suicide victim goes to hell. The Church cannot declare that everyone who commits suicide goes to hell, so we commend them to the mercy of God.
Now we’re getting into salvation theology. Doing a bunch of good works doesn’t cancel out any mortal sin. Achieving eternal life is not a matter of doing more good than bad.