Here "eyes" represents a person's ability to see. For his eyes to grow weary from trouble is a way of saying that he his troubles cause him to cry so much that it is hard for him to see. (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-idiom]])
The writer uses a question to emphasize that if God lets him die then God will no longer be able to do wonderful things for him. AT: "You do not do wonders for dead people." (See: [[rc://en/ta/man/translate/figs-rquestion]])
The writer uses a question to emphasize that if God lets him die then he will not be able to praise God any longer. AT: "You know that those who have died will not stand up and praise you." (See: [[rc://en/ta/man/translate/figs-rquestion]])