You seem to be hinging everyting on communion with Antioch, and as well you should, but take Antioch away and you still have a den of ecumenist wolves in every synod and church.
For instance, chances are you were not baptized when you came to one of the ecumenist churches. This is not because they are using economia per se, they use "economia" as a disguise to justify a person not being baptized. The real reason people are rarely baptized anymore is because they recognize heretical baptisms. This is where the rubber hits the road. You think the ecumenists will acheive a heretical union with anyone by signing "agreements"? No they won't, and they know it. They will only acheive their aims when people start seeing eachother as a "part" of the Church - and what better way than to recognize eachothers baptisms? The recognition of Baptisms is the same to say any church can make one a member of the Body of Christ. I cannot even begin to express how important this is.
But anyway, you seem to be on the right track even if I don't believe you have yet reached all the right conclusions yet.