1. Yes, they’re usually available through the mod section. Just search for a tournament and you’ll be able to find the map pack
2. No, the units in the ram will ungarrison once it dies.
3. It’s a very situational upgrade. Its a defense upgrade: if an enemy converts your unit, it dies instead of switching sides (so imagine you have 2 knights, one gets converted – now you face 1 knight + a monk. With heresy, you only face the monk and can simply kill the monk.
4. I would do that, yes. When playing maa or scouts in feudal age though, “stand ground for your group is better