This poem is about the relationship a boy has with his father and the boy's transitioned relationship he has with his wife. In the poem I think "The Gift" is the father's wisdom. The gift is received when the boy gives his father a kiss, and also the gift is recieved through age and growing up.
The gift is symbolized as the removal of the splinter. Through the gentle tenderness the father figure has when removing the splinter gives the boy the gift of knowledge of removing a splinter. However small that gift may be it is still a gift. When the boy grows older he thanks his father for giving him the gift of being able to remove a splinter- or the gift of wisdom, whether it is recieved through age or through the fathers kiss or both he has this gift and he shares it with his wife. The wife then also recieves a gift, the gift is not the same though it is a gift of relief not wisdom.
The part in the poem about death:
Metal that will bury me,
christen it Little Assassin,
Ore Going Deep for My Heart.
And I did not lift up my wound and cry,
Death visited here!
I do not fully understand. From an educated guess I can conclude that the husband may be boasting about pulling out the splinter from his wife's hand, but I can not be certain.
The end of the poem is simply accepting the gift the boy (now husband) has recieved from his father. The boy has grown and matured. He is able to proudly identify with his giving father, rather than prolong his past identity as a receiving child.