1. I have actually found a yet unknown bug, which was caused by a malfunction of the PHP version your are using. I have corrected it for you via the FTP details. I'm going to update the plugin soon, and I'm also implementing this fix, so it will not happen again.
2. If you have the Search in Comments option enabled on the General Options -> Sources panel, it will be checked automatically: https://i.imgur.com/Abnd14i.png
3. On the Theme Options panel there are lot's of tabs and options you can use to change almost anything you need: https://i.imgur.com/RHHxGZP.png
4. Yes, you can define to search WooCommerce products by selecting the “product” custom post type on the General Options -> Sources panel: https://i.imgur.com/hY5aPn0.pngBest,
If you like my products, don't forget to rate them on codecanyon :)