Split navigation on desktop with even space between menu items

Hello,

I'm trying to do a split navigation with my menu after menu items 3.
But somehow with the code I used, the space on each side of the logo doesn't look even after I apply to code.
I guess it has something to do with the margin-right I used but how to rectifity this so the space on the left and right side on the logo is the same.
 

Here is the store URL: 
https://lion-mouse-mgrf.squarespace.com/
 

// SPLIT NAVIGATION //

.header-nav {
    position: absolute;
    top: 0px;
    bottom: 0;
    margin-top: 0!important;
    margin-left: 0px!important;
}
.header-nav-item:nth-of-type(3) {
    margin-right: 250px!important;
}
.header-title-logo a {
    z-index: 1000;
    position: relative;
}
.header-display-desktop .header-title {
    flex: 0 0 40% !important;
    z-index: 999999999;
}

Can you disable temporarily the code? I think we can achieve split by using another approach

My idea is use JS code to duplicate left nav & append it to right position, then use CSS code to hide some items from left - right nav