That's a serious allegation. Since you made it, you need to tell me exactly how my head is "messed up about EENS."
... claiming that an Orthodox individual can be only materially schismatic due to sincerity ("believing he's in the true Church"). As soon as you see someone substitute "sincerity" for the objective requirements for formal correct faith and formal submission to the Supreme Pontiff, they're subjectivists and are part of the problem not part of the solution where it comes to EENS dogma. Formal/Material Heresy and Formal/Material Schism have nothing to do with "sincerity". You could be the most sincere individual in the world, but you're a Formal Heretic (not simply material) if you don't have the proper formal motive of faith. Material Error and Material Schism reduce to errors of fact, error/ignorance about what the Church actually teaches about a subject and error/ignorance about the location of the Catholic Church.
Protestants, for instance, are all formal heretics, since they lack the formal motive of faith. Orthodox are all formal schismatics because they lack the formal intention of submitting to the Supreme Pontiff. Individuals who are in the Conciliar Church but who are there thinking it's the Catholic Church and who formally intend to submit to the Church's teaching authority are in material error only, and individuals in the Conciliar Church who intend to submit to the man the think is the Supreme Pontiff are only in material error (if they're wrong and these are really Antipopes). That's the difference. If you can't see the difference between the two, then you're lost your bearings on the EENS question also.
Orthodox: has no intention to be in submission to the Supreme Pontiff (but sincerely believes he's right).
St. Vincent Ferrer: intended to be in submission to the Supreme Pontiff (but got it wrong).
These are not the same thing at all.