If you want to maximize your chances to CTB, I advise you strongly to order AEs from overseas pharmacies or to get a prescription from your GP.
It is a matter of life and death, we only got one.
If you fail, you might end up in the hospital and then in a psych ward for days, weeks or maybe months. Awful experience. And you'll be still alive, which is not what you seem to want. Don't make things worse.
The chances of getting permanent organ damage from SN poisoning are low though. If it is a cry for help and a way of playing with life and death, so be it. But if you really wanna leave this world, please think about it thouroughly.