Answers:
1. I would end the conversation by being honest and not tell an excuse to end the conversation. I would appreciate the time the person spent in the conversation by saying something like: "Thank you for sharing your thoughts". And finally I would say a simple: “Okay, take care,” or something similar.
2. The Turn- requesting cues, I would use are: "I'd like to say something" or "er/um".
3. I would say some brief utterances such as "Mm-hm, uh-huh, yeah".