If we concede early then the first leg is basically void and back to square one, but if we get past those early stages then chances will open up for us.
Basically it was one of those accidental trips where a player runs across another, it's unlucky but still a professional foul, because it's all about the forward getting ahead of his defender.
It was, although I've no idea how that isn't a red card. I'd probably have preferred the red at the time, although in hindsight it's easier to say after Vidal scores, I wasn't that confident in him.
I'd imagine most of their players know Arsenal better, probably want to play there as well. That works in our favour.
I'd honestly never heard of this guy, as I don't watch Ligue 1.