Is that theologoumenna as declared before or after a council? Apparently, there were a number of Church Fathers who disagreed with the utilization of icons, for example, seeing it as a return to paganism. At what point does "opinion" become orthodox? And which of the dogmas of the first seven councils contradicts the bodily assumption of the Virgin Mary?
Purgatory, however, as taught by the Latin Church, in some aspects contradicts Orthodox teaching in a number of areas and thus a belief in Purgatory by an Orthodox Christian, in my opinion, would be improper.
Perhaps. But again, what Ecumenical Council binds an Orthodox to not believe in Purgatory? If Ecumenical Councils properly convened by an Apostolic Church declares the existence of Purgatory, then so it exists. However, much of the rest are considered common teachings, not defined doctrine. As a result, God has left room for a future Council to someday settle such other issues.
Regards
" Is that theologoumenna as declared before or after a council?"
Theologoumenna are not matters declared by a council.
"And which of the dogmas of the first seven councils contradicts the bodily assumption of the Virgin Mary?"
None that I am aware of; that's why the Assumption is acceptable theolgoumenon among other reasons.