First if you haven't already, make sure to update to the latest version of the plugin (4.7). Make sure to follow the safe update guide, to avoid any issues.
1. On the Advanced Options panel you can exclude all the categories you don't need, that should do the trick.
2. The connection between custom field groups is an “AND” logic by default. You can change that on the Frontend Search settings -> Advanced panel: https://i.imgur.com/3MF2U5O.png
That should solve this problem.Best,
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