1) When the block reward is gone, miners will get paid from fee!
Current fees are 3% in reward, you will need fees to be 30 times more expensive to give the miners the same revenue and offer in return the same level of protection.
This alone is worth a thing we should give a second thought on, what will be the next phase of transaction fees when all the block reward are no more, could the incentives from transaction fees be satisfactory or give enough income as they have been having of all time, though this is a bitcoin community and i believe one thing is sure, which is the assurance of us crossing whenever we get to that stage.
I don't believe the transaction fees will be enough to keep the system going. The miners confirming the transaction own the transaction fees, and because they still have control of the blockchain, they can easily come together to increase the fees of confirming a transaction, which could be relatively okay at the time because the price of bitcoin will be upped, and they may be more manipulated by coming together and agreeing on a common ground that will benefit them all.