Why can't i have popcorn in the dining room, when i have drinks there. After all, a bar is a bar is a bar. And popcorn goes well with a beer before dinner. Correct?

That would be a question to call and speak with the manager directly. But it is a private business, and tgey do have the right to run their business as they see fit.

The happy hour rules are also different in the dining room vs. The bar area, they are indeed allowed to run it how they wish. I am not the manager but my guess is that it is to limit the mess caused by accidental spills.

Correct I agree