I'm sorry but this has got to be one of the most fustrating contributions I've ever used.
Way too many ajax requests. If 1 ajax requests takes a minimum of 200 ms, then the 6-7 of them I see happening will take almost 2 seconds to finish. Abort the ajax commands whenever you can, or at least do the majority of them when the user clicks the submit button.
Also, what if I decide to prevent all javascript code from running, there would be no database checks before processing, is this secure. Its a great idea for a contribution, just really needs to be updated, because its not practical.
Edit:
Yup, total security issue. I can easily make duplicate customers by ignoring the verifications.