So.. a few things.
1) What VDS plan do you have?
2) What is your servers max players?
3) What is the maximum amount of players you've ever had on your server, excluding yourself?
4) Have you gotten any java breakdowns or miscellaneous errors in the process of running?
5) Are you using the .jar, or .exe version of Minecraft?
I guess I'll start...

1) What VDS plan do you have?
Single Core
2) What is your servers max players?
20
3) What is the maximum amount of players you've ever had on your server, excluding yourself?
4
4) Have you gotten any java breakdowns or miscellaneous errors in the process of running?
Nope. Only when I run from home, and my desktop is better than my VDS but internet is slower (30down/5up)
5) Are you using the .jar, or .exe version of Minecraft?
.exe
Reasoning: I'd like to get everyones comments on this as possible, because once I'm done with my world, I plan on upgrading my VDS so more people can connect.