I would split up your validations. For checking if mandatory fields are filled I would do that in the custom save microflow. In that microflow check all the mandatory fields and give a response to the end user if some fields are left open.
You can then use the widget for those fields like phone numbers that need to be in a specific format. Allthough this also could be done in the custom save microflow with regex checks. Because I might be mistaken but with two phone number fields you will end up in the same situation. As soon as a validation check is done all the fields on the form will be validated.
So my advise would be to do all the validation in custum (sub) microflows before you save.
Regards,
Ronald