That is a tough "cross' to bear" literally....sorry you have that issue to work through. Stand firm in your resolve against the pressure, it will pay off with self respect. I Hope the best for you and family.

I don’t know the details of your friction with your wife and the ages of your children, but I believe that you should be able to explain your point of view to your children and let her express her point of view, and use the experience to teach your kids that there are different ways to view the world and life, and that we can exist respecting the opinions of others. Eventually, with your support and when they are at an appropriate developmental age, they will reach their own conclusions. The best for your children is to see the two of you ironing your differences in an adult, thoughtful and objective way. I think this would be the main and best lesson to learn here.

You are in a painful and a difficult situation if is possible look for professional advice.
Sorry for your lost.

When you say you are having a hard time reconciling your son's self imposed death with your former wife's beliefs, my first thought is that it is not your job to do so. The only thing out of sync that I see are your ex-wife's beliefs and your beliefs. If that didn't bother you when you married, why should it bother you now?

If you mean you are trying to share the peace you have with the finality of the act with her, then I can see how that would increase the friction between you.

When the two of you decided to wed did you have any kind of understanding about how you would deal with religion with your children?

Call your ex to make peace and give it a try if she’s forgiving enough.

She could at least have some respect for you and your view of reality.

If she feels the need for self-comfort by maintaining her delusion, I would suggest that is her prerogative.

As painful as it may be, perhaps the time has come to have "that conversation" with your other kids, that conversation being about the nature of life, the nature of death, and the nature of religion in a rational and informed population.