Featured image size is being restricted–how can I troubleshoot and resolve?

I determined why I was observing this behavior. It appears that, even though I am telling WordPress to display a 750 x 500 px image, it is displaying its own scaled version of the image, which is 750 x 350 px. I have to now go determine why WordPress is doing this. For now though, I can consider this particular question answered.

I still don’t understand the img[Attributes Style], but since it is secondary to my issue, I won’t worry about it.