Not entirely certain I understand this. I was with you up until the part about not having to input all the data into SQL. I think I am missing some aspect of this in terms of where the data comes from.
Yes, you can connect Power BI to SQL. However, it may be possible to integrate Power BI directly with whatever data source the survey tool is putting stuff into.
In general, the process could be that you ingest the data into Power BI into 75 different data models, basically pulling only the data that you need for each member. You could create a template for this and use a parameter to easily switch between the various member organization's data. You could then share these out for free using "Publish to Web".
Another option if you or the member organizations are willing to spring for a Pro license (or if you are willing to invest in Power BI Premium) would be to create a single report and use Row Level Security (RLS).