Will risk sounding like an ad but I created a service for this exact problem because I grew tired of the returns. Size charts sucks and it should be treated as a data problem.

You have shoes at home that fit you well, and I have shoes at home that fit me well. If we have shoes that fit well in common, then I know which size to get in your models. Scale that up to millions of users and the problem of sizing is solved. The service is live, it works and it's collecting people's sizes.

Don't want to post the URL but it pops up when you search for shoe models and size guides on Google. Just wanted to let you know that your wife might be able to buy shoes for you again soon.