Will put all of these suggestions to use! Yes, I've rewarded him (and still do) for the down on his own. I mark it, give it a word. Yes, he sneaked back up on me on the video part, but didn't the previous times. He's being a snot! He knows well what 'down' is... just doesn't like to do it.
The only 'new' thing we're working on is a sit from a down. That he's just learning and doesn't gripe about.
My pug is stubborn/stupid. I've given up on getting her to down. Been trying to teach it every way there is for a year. She will sit, but not unless it's on carpet. Unfortunately, Grim gripes at me whether she's there or not. She doesn't earn any treats when I am working with him. I used a combo of luring the down with food and marking when he was already in a down to teach him that to begin with. He's just always argued with me about it. I'm hoping he will get better. I will stop rewarding him at all unless he does it on the first command, though.