Here "my table" represents being together with David or in his presence. Eating with the king at his table was a great honor. AT: "you will always eat with me" (See: [[rc://en/ta/man/translate/figs-metonymy]])
This rhetorical question shows that Mephibosheth understands that he is not important enough for the king to take care of him. This can be translated as a statement. AT: "I am like a dead dog. I do not deserve for you to be kind to me." (See: [[rc://en/ta/man/translate/figs-rquestion]])
Here Mephibosheth represents the line of Saul, and he compares himself to a "dead dog." Dogs were feral animals, not cared for, and of little importance. A dead dog would be considered even less important. AT: "such a person like me who is worthless as a dead dog" (See: [[rc://en/ta/man/translate/figs-metaphor]])