Hi Ernest,
1. Agreed, unfortunately, with how this site was built, both of these plugins are deeply integrated into multiple parts of the website. Too many hands in the cookie jar with this site if you know what I mean. I have tested this issue with Search + Filter Pro disabled and the problem is still present, so I don’t believe they are conflicting with one another.
2 and 3. I wasn’t able to find any excessively high result counts in the theme, but changing that override method from POST to GET definitely did the trick!!
Thank you so much for your help!