In the Gallery app settings menu, check to see what your setting is for sync by clicking on your Google ID line at the top of the settings menu. I don't know if that will help but something is causing the sync behavior.
For displaying in landscape, I don't see a landscape setting in my Gallery either, but the image automatically displays in landscape when I rotate the phone 90 degrees from vertical to horizontal. Do you have "Auto-rotate screen" checked on in your phone settings (Settings - My Device - Display)?