With respect to part 2 of your post:
First, I didn't think the reasonable classifications test came into play if you passed coverage using the ratio percentage test.
Second, Treasury Regulation 1.410(b)-4(b) states the following -
(b) REASONABLE CLASSIFICATION ESTABLISHED BY THE EMPLOYER.
A classification is established by the employer in accordance with this paragraph (b) if and only if, based on all the facts and circumstances, the classification is reasonable and is established under objective business criteria that identify the category of employees who benefit under the plan. Reasonable classifications generally include specified job categories, nature of compensation (i.e., salaried or hourly), geographic location, and similar bona fide business criteria. An enumeration of employees by name or other specific criteria having substantially the same effect as an enumeration by name is not considered a reasonable classification.
This regulation does not necessarily mean that all job category classifications would be reasonable. It is a facts and circumstances test.