Job opportunities: The only "large" employer in town is Custom Wood Products, which unless you are a skilled wood worker won't be an option. Of course there is a grocry store and other small stores and offices that have non-skilled jobs but they would not be benefit-providing family-wage type jobs. The main places for jobs would be twenty miles east in Topeka or west in Manhattan. For example I work for the State of Kansas in Topeka. Crime is no more or less of a problem than any other rural small town.
Walking town: It depends how far you're willing to walk, for example the grocery store is a little ways east of town, not in the downtown business district. Like all Kansas towns Saint Marys is pretty spread out, not concentrated like towns in the east.
What percentage trad: About half. This relates to your question about farm/homesteaders. Most families who can afford to buy land outside town rather than move or stay in town. Not that in town is a bad neighborhhod or anything but it seems like most traditional families are looking for land. So the population of the surrounding township (Saint Marys Township) is about the same as the city of Saint Marys and is also about half traditional. Not all traditional Catholics in the area are Society people, the Fraternity of St Peter has a chapel and school in nearby Maple Hill and many of the Fraternity people live in Saint Marys (and a few Society people live in Maple Hill)
Mass attendence: All the Masses (including daily) are packed, except 5:45 am daily and 6:00 am Sunday, which are merely reasonably full.
website: www. smac.edu
Homesteaders: See answer above, there are many families who live outside town on acreage (we have 11 acres just outside the city limit)
Family size: All different sizes, some families of one (widows, widowers, young singles) many medium size, many large families (We have nine children, were an item in Pennsylvania, are not noticed in Saint Marys)