Security is required
No, what you call "security" is a subjective appreciation of the hashrate, compared to a perceived "necessary minimal hashrate" that is by no means "required".
The possible gap between perceived and real need doesn't contradict what I said.
There is no "really needed" hashrate threshold that you can compare a subjective appreciation to. The question is flawed in itself.
No. Without massive protocol changes, the market does not have the tools to adapt to this situation.
That's your opinion. Mine is that miners will decide what is theirs to decide. If a group of "core developers" or the "foundation" wishes to hardfork its their problem.
There have been lengthy discussions about this.
There have been quite lengthy discussions about the existence of god too.
a limit will be placed on the total value that can be transacted per block
As in "magically"? or by a hardfork? The context in which you're answering the question isn't Bitcoin anymore, it's a fork of Bitcoin.