Do units spotted only by the Sensor Tower show on the minimap?

Yes, they do.

You're able to see a red dot on the Minimap if any enemy unit is in the scan range of the Sensor Tower.

Enemies will show up as red dots, no matter which team they belong to.
No, critters won't show on the minimap.
Allies... well, they won't show up simply because you will be able to see allied units anyway, they won't be picked up by the Sensor Tower since you already share their vision of the map.