This is not an end to the war, only king Henry's invasions of Normandy proper. Many of your border vassals owe fealty both to you and to the king: a carryover of the turmoils of an earlier age, when the nobles switched fealty from a weaker lord to a stronger Norman one. Henry is within his "rights" in trying to wrest these contested holdings back again; and you are equally within yours, to keep what was given to you by your ancestors. The war continues, albeit, only on the frontiers. Your patrimony has been delivered from a dangerous foe.
The problem of Maine remains: count Conan wants a piece of it, and count Geoffrey's sons are with daddy in trying their best to carve it up. While Maine is in turmoils your duchy cannot be safe.
Invade count Conan's lands to subdue him.
Go to pope Nicholas to appeal for a reverse of your excommunication. Your prestige will be advanced if you are in favor with the church.
Support count Conan's main rival, Hoel of Cornouailles