Hi!
1. I assume you mean this page, but it seems to be okay on my end, I’m seeing 2 columns: https://i.imgur.com/cfxVR99.png
Try clearing your site cache, that may do the trick.
3. Well you can, but the results will very likely not display there. WordPress has only a single search results archive page. If you use Elementor, you should be able to replace the search archive template and customize it. I rather recommend doing that.
4. Sure! Try this custom CSS:
.asp_ss form legend {
font-size: 16px !important;
font-weight: bold !important;
}