Your job is not to write the history of his life, but to make his “today” so beautiful that he forgets all the old memories. When you repeatedly mention his “ex”, you yourself remind him. Don’t compare men with ghosts.
A man always runs after what he can’t have. Be a little “mysterious”; spilling everything can be friendship, not love.
April was absolutely right when he said that when September comes, instead of crying, meet him as a “high-value woman”.