"So man can put asunder what God has joined?"

The church can and does. Google Pauline and Petrine privilege.

"As for the Orthodox, their conditions for economia seem way stricter than what Amoris Laetitia can be interpreted by a particularly liberal priest."

I agree with you here. Cardinal Kasper's original proposal was along the the lines of the Orthodox economia practice as it pertains to marriage. The conservatives hated it. The appeal to conscience and the internal forum approach was substituted instead. Ironically this could prove to be more radical.