.menu-bar {
    -fx-padding: 0.0em 0.666667em 0.0em 0.666667em; /* 0 8 0 8 */
    -fx-spacing: 0.166667em; /* 2 */
...

but menu-bar does not have any -fx-spacing property the correct way would be to use

.menu-bar .container {
   -fx-spacing: 0.166667em; /* 2 */
}