Hi yourgoal,
The listings showing in white are just another CSS issue. You can use Firebug or Chrome Developer Console to look at the HTML to find the relevant section. Looking at the HTML and CSS on my side shows this:
.wpbdp-listing-excerpt.odd {
background: none repeat scroll 0 0 #eee;
}
Change #eee to something else, like a lighter shade of green.
For the category selection box, ctrl-selection is the proper and expected way that users make multiple choices in a list box. Changing to a different control won’t actually change that behavior. You can change the box’s size again by using CSS. I can’t see it directly because you have registration required, but this should not be a difficult change once you use Firebug or Chrome Developer console to find the CSS.
If you’re finding CSS isn’t something you’re comfortable doing on your own, which may be the case from what you’re saying above, my best suggestion to get future minor CSS changes handled appropriately would be to hire WPCurve to help you out here.
They’re WP experts and for $69, you can’t beat their “unlimited 30 min tasks” in a month. This strikes me as something they would definitely be able to fix quickly and easily. They really get these kinds of issues. Here’s how to contact them: https://wpcurve.com