Allowing a user to view/edit only a specific table in a database with ~50 tables
It'll involve 1) removing the user from any database fixed roles like db_datareader (only public will remain), 2) creating a custom role in the DB, 3) granting the new role specific permissions on the one table, and 4) adding the user as a member of the new role. You'll also want to make sure public has no grants to user objects as all users in a DB are a part of the public role.