Vigor means physical strength and in good help. So when the poet says "Her vigor flows like tides in my blood." It emphasises the fact that her well-being is very important to him.
Bitterness in this poem is used to describe the bread that he was given. It can also be used to describe how is being treated and how it isn't very nice. I know this because the author of the poem uses the word bitter. When something is bitter it doesn't have a very appealing taste.
The author uses the word priceless to describe the treasure that is sinking beneath the sand. It means that if the treasure is lost it may never be found again so the author can use this powerful word to associate it with the fact that this object may never be found again.
