1. Red numbers
I disagree. If you have 12 peasants and 12 workers, that leaves you with 0 room for recruiting soldiers or engineers. And it's better to bring attention to it earlier rather than later when you're getting attacked.
2. Yep, not implemented yet.
3. Will make it an option as some people like it.
4. Will fix.
5. I'm not sure why we even allow destruction of armories in the first place, because I don't think we handle that gracefully. There is a separate bug where units will pass through buildings placed after they've found a path, so it kinda makes sense.
Thank you for the interest!