Morgan Stanley say bitcoin mining only profitable above 8600 dollars. I'm not sure this is correct though, especially if future valuations come anywhere close to fruition.
This is not true for every individual as the mining expenses vary from place to place. It mainly depends on the cost of electricity you are using.
This is not correct as far as I know about mining. It depends on the cost of electricity and that of a nice strong system. How much do you spend on hardware? What is the compensation foe the time you spend mining. A one time investment in these inputs and then planning for long term mining will help earn irrespective of the price of electricity and other factors.