Yes, it’s true—I say this based on my own personal, though very limited, experience, as well as (much more importantly!) the consistent teaching of the Orthodox Church—that our prayers and other spiritual work can have a healing impact on others, including those who are no longer in this world but nonetheless alive in and to God. And this would doubtless be especially true for husbands and wives, who were made “one flesh” for eternity by their marriage.
And yes again: those who’ve died—precisely because they are alive in and to God—can help us as well. This is why we speak of a “communion of the saints”, and it’s the reason Orthodox pray for the dead as well as request the intercessory prayers of the saints. Orthodoxy doesn’t believe in “soul sleep”: the idea, promoted in certain Christian quarters, that when we die we pass into a state of suspended animation, only to awaken at the Second Coming of Christ. According to Orthodox belief, we’re still entirely conscious, and we remain aware in some sense of our past life in this world and of the continuing lives of those who remain.
Let’s add this too: Orthodox teach that salvation is a continuing, ever-deepening process, which doesn’t stop when we pass beyond the limits of this world at death. St Gregory of Nyssa used the term epektasis, a Greek word meaning to “stretch out” or “reach forward”. Perfection or deification, he said, consists in an unending epektasis, a continual reaching toward an ever-increasing perfection, as we dive deeper and deeper into the abyss of an infinite God. The Orthodox Christian needn’t fear ever becoming “bored” with a Heaven that’s only harps and nightgowns!