This side-by-side is unfortunately a bit tricky to get right. I suggest adding the headers in a separate HTML section above the first side-by-side section and adjust the width of each column to match the width of the side-by-side columns. Here is an example you can put in this HTML section:
<div style="display:flex;font-size:1.2em;color:blue;"><div style="width:130px">First heading</div><div style="width:180px">Seconde heading</div><div style="width:130px">Third heading</div></div>
To fix the required star when using a hidden column header you must add this to your Custom CSS:
.dffs-formvalidationWrap{
position:absolute;
margin-left:-5px;
}
Let me know how this works out.
Alexander