Do I practice sighting in a pool, no. I can sight just fine, thanks to lots of time playing waterpolo as a kid, etc.
How much does it slow me? Dunno. The only time I sight is swimming open water, and I don't have a reliable way of measuring my speed. It's slower though, and more importantly, it uses more energy.
How much faster drafting, hard to say. In practice, if I'm going second in the lane rather than leading the lane, I'd guess 2-3 secs per 100.
Most people don't do breaststroke in triathlons, so the frequency of breaststroke injuries is going to be lower in absolute numbers. However, you will only get kicked by a freestyle swimmer if you're climbing over their back. I don't do that. A breaststroke kick goes wider, and if you're swimming free then suddenly switch to breast, I might think I'm in a safe spot able to pass, when suddenly I'm not, through no fault of my own.
Leading with your hand is useless if the kick is coming from the side. You've just described why it is more courteous to swim freestyle, (or backstroke, or breast with a dolphin kick, or breast pull, or sidestroke) because someone swimming behind you has a chance to react.
I really hope when you ride you don't deliberately take out other riders if they happen to snooze for a sec and overlap wheels, or even if they're idiots and overlap the whole time. Hell, in an echelon you need to overlap wheels on occasion, depending on wind direction. Yes, if you're overlapping wheels then you are putting yourself in a more dangerous situation, but I've never been in a race where people deliberately took out another rider. Why? Because you'll see that guy you took out at the next race.
How do you determine if a swimmer is worthy of being drafted, assuming you don't know them? My criteria is if they are going a little faster than me if I don't know the other people in the race.
Swimming Workout of the Day: Favourite Swim Sets: 2020 National Masters Champion - M50-54 - 50m Butterfly