If that connection goes down I have this: stratum+tcp://stratum80.kano.is:80
Is it possible for stratum 3333 to go down and stratum80 to still work?
It could be if 3333 is down that 80 will be down as well and what I'm doing is negligible.
I would think so under a certain circumstance. Is it worth it to do that and have another pool for third?
If one port got blocked due to a ddos or other such issues not part of ckpool, then having the 2nd one would help in that case.
ckdb only supports one backend ckpool at the moment and that's not high on the priorities so will be a way off before that's changed.
cgminer itself handles having multiple active and multiple backup pools - as you realise - and that should resolve any pool outages.
P.S. I've switched ckpool over to the latest version already also.