Good tips, though I have recently proven one potential issue. I matched American Customer Satisfaction Index and Glassdoor ratings for 366 companies serving US consumers. There are three retail categories in the ACSI data. Supermarkets have a strong correlation between employee and customer satisfaction. The relationship is much weaker for specialty retail stores and non-existent for the group of 14 department and discount store brands covered. Now, employee happiness and employee engagement are quite different concepts. Employees can be happy with their commute to work, their pay and the food in the company restaurant. None of these do anything for customers.
My blog post on the research includes links to all of the data and is here.