If segwit ends up having bugs, as some suspect it might, bitcoin cash is the logical replacement as every bitcoin older will own same number of coins. If that happened (segwit disaster) every bitcoin holder will support bitco7n cash, and with larger block size network scaling problem is taken care of.
Bitcoin cash is a segwit insurance policy.
Since a lot people sold their BCC, I don't think they will consider BCC as a backup of BTC even when segwit ends up having bugs.
Yes, but those who sell their BCC made their choice, just like someone can cash in a life insurance policy for instant cash sometimes, and then forgo the insurance cover the policy entitled them to.
If segwit blows up BCC will take over, or at least there will be strong momentum from majority for it to do so.