Thankfully we didn't get an even earlier start date. It was only some time ago that the same Umayyad dynasty in Andalusia used to be known as Umayyad Caliphate, controlled entire Muslim world as a single entity and was THIS large. Even Pope would shiver in his boots when thinking of calling a Crusade on them.
Abbasid revolt changed it all and reduced them to Andalusia.
Indeed, I agree with you. Marriage is the only way I found to keep the empire together for at least a hundred years, when it would become a de-jure land. I would also focus on liberating the Iberian peninsula (and then giving them independence) to ensure I face no Jihads and the unending train of 200-man armies coming in from far reaches of Persia.
At the moment the biggest problem is Slavic revolts. They just don't stop, pop up a few months after I crush the last one, and drain my levy to zero. I wish crushing revolts had some influence on