You would usually design the spell with particular bugs in mind. A swarm of spiders won't have the same stats as a swarm of scorpions or bees... if you want versatility... that's extra magnitudes, which will in turn reduce your penetration and make it harder to research, so it's rarely worth it at that level unless you're very specialized (and if you're very specialized, it's often worth it to spend an extra season to learn the extra spell anyway).
Yes. See Octavia's one thousand legions for a spell almost identical to what you describe, just with an extra magnitude for size in case you want to confront armies. Note that such a spell may have to be a Ritual (due to its "massive" effect), depending on the troupe's judgement; a sufficiently "small scale" version would not be, however.
Well, there's a caveat there. Because Range is Touch, you can only provide new directions to the little critters when touching them, including upon creation. So you can create them and assign them a task, but you can't control them with magic from afar. Though you can certainly assign them a task that includes returning to you for new instructions at the end, and perhaps a task to follow simple visual instructions if you remain within sight of them (e.g. move left or right, forward or backward, depending on whether you are raising your left or right arm, both or none).