Lol you have habits you don't know about ... You must have used it to check mail so there it is! Can't you change that in the Cover settings? If you can't then the app sucks! Unless the paid version (coming soon) will have the options. You'll have to wait and see. Or dump it. I wouldn't accept that.
In your Google Account settings on your huge phablet you are usually presented with the various services that Google provides. Amongst them is gmail. Just opt out. Your calendar, contacts, Hangouts etc will remain active and still sync. And the gmail app itself, you can also sign out. It won't affect the rest of the Google settings.