“no chance of redemption and forgiveness of this mortal sin”Some folks are in such pain and bad enough health that they are willing to take the chance you are wrong. Life (and death) is risk.
God told Moses to go up a mountain and die there. (Deuteronomy 32:48-50) And from this, I think that prayerfully refusing life-extending medical care (trusting God to keep you alive) is not the same as murder, nor is it that of a person thinking irrationally. However, such is rare, and purposely committing suicide is murder. And sadly, many do so imagining that will be a relief from pain - to their horror, having died in their sins.
As regards not thinking irrationally. Dear mamma please don't die is one case. She was severely depressed, seeing herself as a failure over things like the kids did not clean their room well, and the doc. gave her pills.
Too depressed to go to church on Easter with her family, or even dress for it, she saw the shiny green pills in the medicine cabinet, and the thought came that she should take them all and thereby do everyone a favor (after all, she blamed herself for all the failures she perceived).
At first she resisted, but soon went back and took them.
Then she put a ham in the over, so that the family would come home and have a nice Easter dinner.
Rational? I think not (not that I always am in all my choices).
Meanwhile, her husband at church, who was not one to experience inner impressions much, felt moved to get home quick, and gathering the kids do so, and found her slumped on the floor in her nightgown. He immediately got her to the hospital where they pumped her stomach.
And while the doctors thought she should have been left in a vegetative state, yet by the grace of God she recovered, and wrote this short (190 paperback pages) book, to help others. About $10 at Amazon. Thank God for his grace.
I am of the saved by grace, kept by grace camp.
While assurance of salvation is certainly never a license to sin, ever, and that deliberate sin will certainly have to be answered for, I do not believe that even if one commits suicide, they forfeit heaven and are condemned to hell. That would be a saved by grace, kept by works theology.
There’s a difference between loss of reward because of behavior and loss of salvation.
Not to mention that it’s not just physical actions that are sin. Jesus raised the bar impossibly high in Matthew 5-7, when He taught that even the thought or desire to sin was the same as doing it.
At that rate, almost all of us would be guilty of the sins listed in Revelation that you state condemns someone.