Don't worry too much at first with the distribution. In fact, I think it its well distributed. I didn't expect an extractor, but it makes the game easy to begin (is it also made with Launch4j?). Maybe there's another work-around: an installer. I've never achieved nor the former nor the latter. I cannot give you any advise because me (and I think many others) have faced similar distribution problems. In my case, what I usually do is to pack libraries and natives on JAR building. Then with Launch4j I pack it into an EXE file and then on the same folder I put every other resources. I couldn't find a way to also pack the JRE with Launch4j. I've seen you packed the JDK. Couldn't it be sufficient with the JRE? I think this is a contiuum problem for almost every people that works with Java and even more if we are working with natives... By the way, since you talked about Mac, the distribution problem gets even bigger on the window system from GLFW. That's another pending task for almost everyone that works with LWJGL.
I encourage you to publish it on TIGsource Playtesting forum if you haven't already done it, so that you receive more feedback. I see you have a webpage. I can confirm you I now admire your work.