A MEU has enough supplies to sustain itself for a week. In a situation like this they could stretch it out to a month or two on the outside a year. Fuel and ammo are finite.
If I were the MEU CO I'd get on the ships and sail back to America go to Titusville, Pa and drill for oil. With oil all things are possible. Within a few years you're self-sustaining and then go back to Rome.....
Not if they think God was going to resupply them. Working on their religions and superstitions is how this battle will get won. If they think God was sending these men then they would follow with God will see them taken care of, the CO would play on that completely. I still think a merger without violence would be possible, allow the emperor and senate to remain in power, just with some changes.