Very cool
Only one criticism, and it's only because you're doing such a good job staying faithful to the original board game.
In the original board game, marines are allowed to move through each other's spaces, so long as they don't end their turns in the same space.
This tripped me up a few times the first time I played your version.
Oh, and the Operations scenario - in the original rule book, it states that Ripley *must* move Newt down the hallway at her first opportunity. (She can leave Newt there and return to the fight, tho.)