The flowers he "nearly bought" could be refering to the future they almost had together. She may not the refering to the regret she had for the relationship, but rather just a sense of bitterness, of how it could have been.

Unfulfilled promises, this man is capable of saying but not of completing the task.

The reference to "the lovers" here could be a reference to the author, or the character he's representing, himself; that he is writing for people that is similar to him.

If this represents the death of one (or both) lovers, the silence here would not only be in their control. They stay silent because that is the only way to show their love to each other.

This could be the reference to a inevitable, painful moment that is bound to happen, and in this sentence the author uses a very interesting comparison of fate to "a blue thread", bound to be loosened. This could suggest regret, sorrow or even acceptance

Bosom here could be understood as the care, and in this sentence he could be refering to how their relationship is at stake

In this sentence, other than the life that her finger give, the author could also be referencing the gentleness of her touch, the colors of the mentioned fingers.

I think this is a very interesting take on the "sparkle in the eye" of a human being, could be a metaphor for innocence.