... When I test in the Xlights program only the first 4 lights work. ...
I am also somewhat new to xLights (less so to pixels). However, I saw essentially the same issue when I had accidentally left my raspberry pi (running FPP) sending output to the pixels, and also had xLight set to "output to lights" (the last icon in main bar, by default).
I think that xLights and FPP were both sending data over wifi, just that one was sending an all-off signal slightly later than the first was sending the pattern. Thus, a few lights went on, then flickered off, (repeat).
It may not be your issue, but worth checking. Good luck!