That looks like a bottom margin added via a 3rd party CSS, but I can’t tell only by the screenshot. You can maybe try this custom CSS to negate that effect:
div.ajaxsearchpro.asp_sb fieldset.asp_filter legend {
margin-bottom: 8px !important;
}If that does not work, then I can try looking at it directly, just send a link to the page where the search is visible.
Date filtering via range sliders is not possible.