Can I say "no more" instead of "no longer" here?
Yes, you can say "no more" instead of "no longer" in this case. "No more" and "no longer" in this context are used to express time, and have the same meaning. However, in other contexts, there can be a slight difference in meaning. "More" expresses quantity, so in some contexts, "no more" means no more amount of something. "Longer" expresses duration or length, so "no longer" is often used to mean no more time or no more length. Ex: I can eat no more than four slices of pizza. Ex: I can afford to stay here no longer than a week.