Your instuctions on attaching an image are fine but the image is too big and needs to be resized. I'll leave that for now and tell you some things that I have done. Since I believe that the only images on my tablet are on the external card, I've removed it. I've reformatted it and reloaded the pictures but left it out of the tablet for now. I suspect that an app in the tablet is "harvesting" the pictures on the external card and creating thumbnails on the internal card. I've found that, in my google account settings there are various tickboxes including "Sync Google Photos" which was ticked. I've unticked it. I'm not really sure of the significance of that but the situation as of now is that the tablet is stable ie NOT creating thumbnails and NOT running the battery down.
I'm planning to laeve it like that for a day or two and then plug the external card back in. I'll repost when I do.