Your son would live a happy life? Or your T would? I'm guessing you mean he said that your son would have a happy life?

Sure, people can and do survive experiences of suicide in their relationships. But they WILL be forever impacted by it.

I don't know why your T would say such a thing. Not a method that I'm aware of. No one has ever told me that a person would be okay if I died. Well, except for themselves. L tells me my death would forever impact her AND she has good self-care and support that she would go on living a good life. But that's different. I do know that sometimes people might try to guilt you into living, but this isn't that either...

I would definitely talk to your T about it. Maybe it was a defense mechanism somehow? Somehow it was meant to be reassuring? It's best to talk it out because if you're ever unstable again, you'll want a more helpful response than that.