1.) When you think of them and don't immediately have a need to see or call them. (That for me was quite a long time)

2.) It's a tough call in a parasocial environment. But I would say (if you are a really strong person looking to feel more normal) immerse yourself in memories of them until you feel terrible but not suicidal. Then give yourself at least a month to try to not think of them. Then when you are ready to immerse yourself again, don't just look through pictures or a video and realize you don't feel terrible like you did before. That good feeling of a beautiful memory with them leads you to feel good when a fleeting memory goes through your mind instead of the spiral it likely is right now.

That's the best I've got, lost my dad in '07 and that's what I did. I hope you have an easier time than I did.