Hi @rmk1138! Sorry for the delay replying here.
About the gallery problem, the app I can suggest using is Files, which allows you to browse all your ownCloud files. It’s not a specific gallery app, but could do the work. You can also find this app directly linked from Settings > More > Access document provider. More info about this in this thread: How can I access my owncloud local files with another app? - #4 by Juanca
About available offline files that re-download when you open them, I saw you opened an issue (I think it’s you 
), so let’s keep track there.
Any more doubt don’t hesitate to ask us! 