1. In some cases you will have to change the input field background as well because it might overlay the whole search bar. You can find it on the Theme Options -> Input field layout panel: https://i.imgur.com/EDHtvJt.png
2. It might be possible.
I've looked up a support thread where someone was using the social feather plugin, and I was able come up with a solution to include the icons on the front-end results: https://goo.gl/C6yk66
Other possible resources:
One is to use a filter to modify the results content to append the extra html code of the icons there. There is a tutorial on how to add WooCommerce add to cart buttons to results, which I believe is a good starting point: https://goo.gl/pVye7e
Another one is to directly edit the plugin template files. Here is a detailed guide on how to do so: https://wp-dreams.com/knowledge-base/result-templating/
3. On the General Options -> Sources panel you can select which post types to include. I believe you only need to enable the “Search in posts” option in this case. If the blog posts are in a specific category, you can also set up to include items from only that category on the Advanced Options -> Exclude results panel: https://i.imgur.com/ku0MbUD.pngBest,
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