Should I give this letter to him? What do you think?

I think you should go for it. Give him the letter as soon as you can. Why not? The worst that can come out of it is that the two of you won't be together and you're already not together so you've lived through the worst of it. This life is too short not to take chances. Give him the letter and never regret doing it, as they say 'It's better to regret the things that we have done, rather than the things that we haven't done.' Good luck!