Should I send my goodbye messages to him, then block him on WhatsApp immediately, or wait for him to read it and respond before blocking him?

I have been talking to him for 4 years, he left me last year but we still talk like lovers and it's like our relationship has been going on for 4 years. but for the last 1 year no matter how much I begged him to save the relationship he didn't return to the relationship. he never calls me girlfriend since he left me, but he calls me as his love. he says "my love" to me, even in his phone i saved as "my love". he always say "good morning my love i love you" and "goodnight my love i love you", we still chat everyday 1 hour like lovers. I begged him again last week to save our relationship but he said he can't be with me even though he loves me. what should I do in this situation? I am also thinking of asking him one last time, like are you sure about your decision but I don't know exactly what to say or do. what should I say to him? I want to ask him one last time if he thinks about continuing the relationship or not and ask him if he is sure. And then if he says no. I am thinking of sending him a goodbye letter that I have prepared. But what should I write in this letter? Since our relationship is long distance, it will be a digital letter, in other words a pdf. Should I block him right after sending him this goodbye pdf? We only talk on WhatsApp but he also knows my email address. Actually I want to save our relationship but I think maybe if I make him afraid of losing me he will come back to me because I begged him for 1 year but nothing changed. Should I block him before reading that my goodbye letter (my goodbye messages as pdf)? For example, should I send it and then block him immediately so that he has a fear of losing me and understands that he can lose me too also? just like since last year everyday i afraid to lose him. Or should I block him after he reads the goodbye pdf of mine and responds to me? What should I do? I will send it via WhatsApp. If I block him without reading those messages (when the messages are delivered), he can read that pdf, right?
Should I send my goodbye messages to him, then block him on WhatsApp immediately, or wait for him to read it and respond before blocking him?
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