Yes foot down before release and yes glove side foot.I think you need to define "throw". The foot is always down well before release, but if you're talking about breaking the hands / ball out of glove, that's much earlier in the overall throwing motion.
Also - stride foot = glove side / front foot?
I have kids throw a volleyball. It's in order to throw it directly at your target, you HAVE TO keep your hand behind the ball. Have seen girls with awful motions throw a volleyball twice, and on the second throw, it's just beautiful.I think, but cannot prove, that they often drop that elbow in an effort to get under the ball because it's too big for their hand (or they think it is/learned to throw that way when the ball really was too big for their hand). When I see the elbow drop, it almost always comes with the palm of the hand pointing toward the sky with the ball sitting on top.
Maybe working on staying behind the ball could help? Very difficult to do so if you're bringing that elbow down too much.