I am very sorry about your loss. This must be unimaginably painful. I hope you can eventually make peace with what happened.
I kind of get your intentions. They are good intentions. But the way you express them is not helpful and it is extremely unlikely to work and actually stop someone committed to the idea of leaving this world from doing that. It will only make the already suffering person suffer more.
And yes, same goes to your claims about the incredible painfulness of certain methods, legitimacy of which I now question. It might discourage someone who is impulsive about their decision, and yes - such cases do happen, even here. But the vast majority of people on this site are either chronically suicidal, or in a situation when they spent an extensive amount of time researching methods, i.e. it is not an impulsive decision at all. If you scare them out of a method, they'll use a different one. I am not saying that all hope is lost and no one here can be talked out of ending their lives. But your kind of approach is very unlikely to work.
It might be a painful thing to hear, but people on here cannot work as a substitute for your lost loved ones. It is okay to feel anything you feeling, be it anger, resentment, confusion, sadness or loneliness. But directing these feelings at strangers is not going to solve anything and it is simply not right. None of us has anything to do with your loss and none of us can make it better for you, unfortunately. We can provide some perspective on what serious suicidality is like, why it can happen and why family doesn't always hold people back from ending their lives, but that's only if you feel ready to listen. If I could "donate" my parents to you, I would happily do that without a shadow of a doubt, maybe that would make both them and you happier. But unfortunately that is impossible.
A site full of suicidal people is not the world's best place for someone processing their grief over a suicide of a loved one, but you can make your own thread and share your feelings about your own situation or maybe ask questions that has been bothering you. But please don't try to scare or guilt people, it will do no good and will probably get you banned.