I've noticed that most of the games come to an end base race (on mid lane).
Yes, it happens but not often
Stacking on mid is just best way, I bet most of players in real League do it
Yes, I also use the group for 15 minutes, just get my team pushes their T1 and they are mine. And so to the nexus, and then one of the teams back
Have you got a game replay you could show us? Would help a lot to see exactly what you mean :)