What does it mean when someone says:

I think "ka na lang" means "just you" ... there is a nice song "akin ka na lang" which translates to "You just belong to me" .... maybe this helps ... I am not so sure if this translation is applicable in the context you found the phrase ... but mabye some native filipino speaker know better than me ...

Also not a native speaker, but I wonder whether this person is using "shh" as a verb--sort of like you can use "shush" as a verb in English, to say things like "she told me to shush". If that's what's going on, then the second sentence here means something like "Just shush".