a rogue Scottish agent (do we know him from somewhere?) killed off everyone who worked for Torchwood 3 in 1999, so that they couldn't see the "coming storm"

I gathered from the ep that Alex was the leader of Torchwood 3 and he mercy-killed his team, then gave Torchwood 3 to Jack?

Tosh built a sonic screwdriver from scratch?

Isn't it a sonic modulator? I doubt it has all the capacities of a sonic screwdriver, I think it just makes loud sonic waves until someone's brain goes boom.