Opening Door

Opening the door allows heat and moisture out. There's no "rule" of how much because it depends on too many factors. Keep it to a minimum.

It's not the moisture escaping that's the issue, it's the heat.

You can do them all at once, but everything will get dripped on by the stuff above and maybe change flavors (not a big issue for me).

Don't put chicken above anything. Let's gray streaks on whatever it drips.

NEVER put wet wood in a CS, doesn't help and smoldering wet wood isn't your best source of smoke.

SmokinOkie is dead on...it is a heat issue.

Keep in mind that when you open the door, you increase your cooking times on the meats remaining inside. Obviously the oven has to get back to temp and this can take time, especially when you have a full smoker.

Also be careful on adding more wood. Too much can really overdo the flavor.