Flatiron: Restrict gallery columns to 3 above a certain width

Site URL: https://www.kwerling.com/

Hi!  My portfolio uses the Flatiron template, where the homepage is a gallery of all my project pages.  I only have 6 projects at the moment. They look good in 2 rows of 3 columns, but I really dislike when it jumps to 4 columns on larger screens and the second row becomes half empty.  I'm fine with it flexing to 2 or 1 columns on smaller screens.

I would like to restrict the home gallery design to 3 columns at 1440 px wide screen sizes and above.  Screens smaller than that I would like to leave responsive.  How can I do this?

Add to Design > Custom CSS

@media screen and (min-width:1700px) {
div#grid {
    height: auto !important;
    display: grid;
    grid-template-columns: repeat(3,1fr);
}
#grid .item {
    width: 100% !important;
    height: auto !important;
    top: unset !important;
    left: unset !important;
    position: relative !important;
}
}