1) I think its because that carbon is electrophilic, it has only 6 electrons instead of 8.
2) Yes, you can see it on the next step
3) Im not sure, here but I would say its because having O+ is unstable, so is Cl+ but it breaks then.
The bond breaks because there are 2 highly electronegative atoms on that carbon and AlCl3 even increase the polarity of Cl-C bond