Ok I hacked through this but it turns out that the DB Abstraction plugin was not correctly replacing the column name PUBLIC with [PUBLIC] in the queries. The problem is in MSSQL ‘public’ is a reserved word and should be enclosed in brackets to mean a name.
So I changed all queries containing PUBLIC with [PUBLIC] in the testimonials-widget-admin.php and testimonials-widget.php files and it fixed my problem.
I’ll mark this resolved since it fixed my issue, though moving forward I’ll have to re-write this if I update the plugin.