The validation rule needs to go on the date field in the repeating table itself. The first condition should be if the field is not blank (to prevent false errors).
Then add your second validation rule.
InfoPath won't let users submit if there are validation errors in the form. However, based on this description, it sounds like you may have some other rules that are executing even if the form cannot submit. You may need to add some logic to count the instances where the date field is not valid.