I'm not sure what you mean by intellectual. Let me try again.
We have 2 forms of the Roman rite, the ordinary and the extraordinary. The Roman rite is practiced whenever either is celebrated. That is an example of "unity of practice" that has "various ways" of being performed. Communion in one form is the same communion as in the other.

Your questions are all good ones, and I have no idea if I can answer them.:
with marriage, the differences between Poland and Malta are fewer than the differences between the extraordinary and ordinary forms imo. If I am right, it is an example of what Francis refers to in AL. There is no disruption in communion if there is none between the two forms of the Roman Rite.
AL is in a certain sense a collaborative effort between the synod and the Pope. I am not sure what you are asking.
RC teaching on divorce has long distinguished us from most other Christians. I don't see why a deeper understanding would impede ecumenism.