The burr would have been created due to wear. Honing the cylinder just made the whole bore bigger to match the wear. This is not good. It may "work" right now but, for how long?
Please, for your and other's safety, get a new one!
Rearview mirror goes between the two sun visors. You'll find there is not much side to side variation possible. Height is set by what gives you the best view out the back. Bear in mind that it's not so low as you bang your head on it when you enter.
The brake light is turned on by either a level sensor in the reservoir cap, or the brake shuttle valve with a plastic switch in the centre of the valve. If your car has a brake shuttle valve, unscrew the switch and use a small screwdriver to centre the valve. It's centred when the high spot is centred. Screw the switch back in and the light should be off.