The problem is NOT with sola Scriptura, but with how people define what it means. Most who reject the doctrine get it wrong. As the ONLY resource we have that is 100% Divinely-inspired, God-breathed, Holy Spirit revealed truth, the Scriptures ARE the authority by which all truth claims must be measured. If someone declares Christians MUST believe the universe revolves around the earth or they cannot be saved, we could reject it because it is NOT something God's word teaches us nor is it something God tells us is a major tenet of the faith - not to mention it cannot be shown to be something Jesus or the Apostles taught nor can it be found in either the Old Testament or the New Testament writings.
Since the first century, Christians have believed in basic doctrines that define the Christian faith and they are ALL proven BY sacred Scripture. Scripture DOES interpret Scripture and the heresies that arose from the start WERE disputed BY Scripture. God's word is the highest authority we have because nothing else is Divinely-inspired truth. It was good enough for Jesus, His Apostles and the early Christians, it is good enough for us and IS our authority to which we owe obedience. The church (believers) is not in authority over God's word - just the opposite.
However, as you state it, your position ignores, first the point I made in my last post, that a hermeneutic tradition is needed in addition to the Holy Scriptures because they do not interpret themselves (yes, you assert they do, but I'll comment on that in a moment), second the role of the Holy Spirit, and lastly history.
As to the first point, the notion that "Scripture interprets Scripture" is the motto of a particular hermeneutic tradition given more full expression by the Anglicans in their Thirty-Nine Articles of Religion in Article XX (a statement of a mild version of a sola Scriptura position) which says of the Church, "neither may it so expound one place of Scripture, that it be repugnant to another." This is, in fact, a statement of an important feature of the usual Christian approach to Scriptural interpretation, but that this approach is the correct one is not, itself, provable from the Scriptures.
Other, contrary, hermeneutic traditions exist. The heretic Marcion, for instance, approached the Scriptures very much in the spirit of the latter-developed Muslim notion of naskh -- later Scriptures abrogate earlier Scriptures when there is a contradiction -- so that for Marionites the New Testament blotted out the Old. Gnostic heretics took similar positions.
And even within the broad outline of "Scripture interprets Scripture" one does not arrive at a single authoritative truth without making judgements -- both those of us who believe in the reality of the Eucharist as Christ's very Body and Blood and those who regard it as merely a symbolic memorial point to passages of Scripture and argue that their interpretation is the one which correctly expounds Scripture (without expounding any point in a manner repugnant to another). This, of course, brings us to the next point, the role of the Holy Spirit.
Saying, "The church (believers) is not in authority over God's word - just the opposite," with its reduced notion of the church, is quite true. But the Church, the dwelling-place of the Holy Spirit, does have authority over the Scriptures: it was the Church which decided which of the numerous writings prophesying of and testifying to the earthly ministry of Our Lord God and Savior Jesus Christ constituted the Canon of Scripture -- not by the authority of believers, but by the power of the Holy Spirit. We Orthodox Christians in our hymnography speak of the Fathers of the Holy Ecumenical Councils as the "harps of the Spirit", attributing their infallible judgement of doctrinal truth (seen only in retrospect by the whole of the Spirit-bearing Faithful assenting to their judgements), not to them as believers, but to the Holy Spirit, who (as the Creed says) spake by the prophets, and who Our Lord promised us would lead us into all truth.
We know that the "Gospel of Thomas" is not Divinely inspired Scripture not because an analysis by discursive reason applying a "Scripture interprets Scripture" hermeneutic tells us it contradicts the canonical Scriptures, but because the Church, led by the Holy Spirit, recognized it was not Divinely inspired and left it out of the canon of Scripture. Had the Church judged otherwise, your hermeneutic principle would be obliged to find variant interpretations of both it and the canonical Scriptures to remove the apparent contradictions, and would not discover its lack of Divine inspiration.
It is the Church, guided by the Holy Spirit, not the text of the Scriptures themselves, which provides the correct interpretation of the Holy Scriptures. I recall Fr. Chad Hatfield telling me about discussions he had with a group of Lutheran pastors contemplating embracing the Holy Orthodox Faith. They pressed him on whether the Orthodox Church agreed with the notion that the Scriptures was the complete and sufficient rule of Faith. He agreed, with the proviso: provided they are interpreted as the Holy Orthodox Church has interpreted them.
Nor is it the case that the Holy Apostles proved their doctrine solely by appeal to Scripture, they also proved it by the power of the Holy Spirit -- Peter's shadow healing the sick, for instance. And, to the extent they did prove doctrine by Holy Scripture, it was by providing argumentation that the prophecies of the Old Testament, the Scriptures accepted by their Jewish and God-fearing hearers, pointed to events, as yet not recorded in Scriptures, in the earthly ministry of Our Lord Jesus Christ.
The Holy Scriptures are the Church's books, some inherited from Israel, the Church of the Old Covenant, some authored under the inspiration of the Holy Spirit within the context of the life of the Church of the New Covenant -- the Gospel was preached by the Holy Apostles before there were written Gospels to record it, the letters of the Holy Apostles were mostly reminders of things said face to face before they were set down in Scripture. The notion that the Holy Spirit stopped leading us into all truth when the books of the canon were fixed cannot be proved from Scripture (which contains no notion of what the bounds of the canon are), and in the Church's experience is simply not true. The doctrines of the Seven Holy Ecumenical Councils and even the canon of the Sixth Ecumenical Council that fixed the canon of Scripture are all Divine-inspired truth. The anaphoras of St. John Chrysostom and St. Basil the Great (look them up and read them) are Divinely-inspired truth. Do any of these contradict Scripture? No, but Jesus's promise concerning the Holy Spirit is still active today, and has been all through the long history of the Church since the day of Pentecost in year of His Saving Death and Glorious Resurrection.
Finally history -- the only Scriptures Jesus, the Apostles and the earl(iest) Christian had were the Old Testament, which, by the looks of how it's quoted in the New, they read in Greek in the Septuagint. The Four Gospels, the Acts of the Apostles, the various Apostolic letters, and finally (and controversially) the Apocalypse of St. John the Theologian, circulated, were copied, read, and (again thanks to the Holy Spirit) generally accepted as true testimonies to Our Lord Jesus Christ, from their authoring until they were finally listed by St. Athanasius of Alexandria in a letter in the mid-fourth century and included in a canon of the Council of Carthage in 419, along with the entire Septuagint, in reaction to the Marcionite heresy, which canon was finally given universal force by the disciplinary session of the Sixth Ecumenical Council in 692.
So, a little question: do you accept as canonical Scripture The Third Book of Esdras, The rest of the Book of Esther, The Fourth Book of Esdras, The Book of Wisdom, The Book of Tobias, Jesus the Son of Sirach, The Book of Judith, Baruch the Prophet, The Song of the Three Children, The Prayer of Manasses, The Story of Susanna, The First Book of Maccabees, Of Bel and the Dragon, and The Second Book of Maccabees?
And if not, by what authority? They were good enough for Jesus, His Apostles and the early Christians.