Obstoacles to synod and concordia

At the risk of sounding heretical, I will say that the way back to synod and concordia will only be found by returning in humility and child-like faith to the Giver (Jesus) and His gifts (word and sacracment). In my experience, there are two major historic (LCMS) obstacles to reaching this blessed end.
First, We were taught with great certaintly that the doctrine upon which the church stands or falls is justification by grace thrrough faith for Christ’s sake, aka forensic justification. As Dr. Jack Preus, Jr. points out in his book on Biblical Metaphors for Jusitification, however, this is only one of many biblical metaphors describing how we are being saved by the person and work of Christ. Yet we have made the whole enterprise stand or fall on this one aspect of the truth. This begs the question, if I am declared righteous for Christ’s sake, why do I need Holy Communion? What good can it possibly do for me? The way Luther’s Large Catechism speaks of the Sacrament of the Altar was not reflected in the teaching and practice of the LCMS in which I was raised. Until we see the whole life and mission of the Church flowing from and returning to the Eucharist, I fear we will remain divided.
Secondly, we were taught with great certainty that we have the pure doctrine. Aside from the problems of triumphalism inherent in such a view and its somewhat unscriptural base (we see through a glass darkly — if we say we have no sin, we deceive ourselves, etc.), it leads us to the false assumption that it doesn’t matter how we practice so long as we believe correctly. Ironically, the questionable proposition of pure doctrine splits asunder what the church desperately needs to hold together: the law of prayer and the law of belief. I am not trying to say that we cannot know and confess true doctrine, but that we cannot claim to have it “pure” apart from our worship and life.