Random, I understand that you are looking for older staff, but I think you are receiving a small amount of replies because of your age limit. I think you should lower it to 13, therefore, you won't get really young audiences yet still get young people. I feel that there are people who are eager to learn and become staff of servers but are turned off by age limits. Trust me on this, you can find extremely responsible and mature people who aren't even in high school. Take me as an example, i'm only 14 yet I have had the experience of staffing servers for 6+ years in MC, I can run servers at a highly organized level.
I am not interested in any positions and I just felt like bringing this to your attention. Anyway, good luck on finding staff members.
