Go to settings scroll down to "sound" app and open it up. It should give you the option to assign sounds and volume to phone, media, notifications, and one more I forgot. Make sure you're volume is up enough for notifications of text messages to be audible.
I want text to have its own sound, So not 'notification ' sound. Is that possible on this samgsung? Would also love call volume as it's own thing, not tied into media volume so I don't have to tell every caller to wait while I turn up volume. Any ideas?
Sounds like you've reached the end of ideas from me. Perhaps. Samsung can help you. What I suggested to you works for me (Google account) I'm not familiar with Samsung. Ask Samsung