I would reassure you first that you’re not alone. I receive messages with some frequency from Orthodox, both clergy and laity, who are deeply interested in the perennialist school but who feel they can’t really talk about it with their priests or hierarchs. A few of the laity want to argue with their priests, and I always make a point of emphasizing that we go to Church to receive the Mysteries, not for a lesson in comparative religion: a spiritually serious exclusivism is much better than a banal and fashionable ecumenism.
It should be pointed out, second, that the perspective of the abbot you mention is not that of all Orthodox Christians, nor are the writings of Father Seraphim Rose, which he apparently cites, universally regarded as having the authority his spiritual children, quite understandably, may attribute to them. Orthodoxy comprises a much wider spectrum of theologoumena on such subjects as universal salvation than it seems your mentors think. Metropolitan Kallistos, for example, while by no means propounding a definitive teaching, is nonetheless quite open to the idea of universal salvation; he goes so far as to say, in The Orthodox Way, that even Satan may be saved; and he answers the question he poses in the title of an article called “Dare We Hope for the Salvation of All?” with a resounding affirmative, quoting in so doing Saint Silouan: “Love could not bear that…. We must pray for all.”
Also worth considering is the fact that Holy Cross Greek Orthodox press saw fit to publish the late Philip Sherrard’s final book, Christianity: Lineaments of a Sacred Tradition, in which the author explicitly espouses the idea that there is a transcendent unity of religions. I might mention too that when I sent a copy of one of my own books—Paths to the Heart: Sufism and the Christian East—to one of the monks I met last summer on the Holy Mountain, he wrote back to say that he had read it appreciatively, passed it around to other English-speaking fathers, and would be placing it in the monastery’s library. None of this is to say, of course, that this man is, or will ever be, a perennialist, but it’s clear that his Brotherhood would not refuse me the Mysteries simply because of my opinions on this score.
Now I suppose all this “evidence” would only lead some people, perhaps your friend the abbot, to start raising questions about who is really Orthodox. I am well aware, for example, that Metropolitan Kallistos has his detractors, among some Old Calendarists at least and perhaps elsewhere as well. And Sherrard is undoubtedly a very controversial writer. So I’m certainly not suggesting that these facts will sway every interlocutor or that you should adduce them in endeavoring to argue with fellow Orthodox. All I’m trying to do is to help bring some peace to your heart with the encouraging news, if it is news to you, that Orthodox Christianity is a subtler, and larger, reality than some people may realize.
I’m reminded of a maxim I heard back in the mid-90s when I was visiting Saint Paisius Abbey in Forestville, California—a maxim that came, let me add, from none other than the abbot, Father Herman Podmoshensky, Father Seraphim’s old friend and the co-founder of the Saint Herman of Alaska Brotherhood: “Being Orthodox is what counts,” he said; “being thought to be Orthodox is merely a luxury!”