"Why should I believe the Council of Trent was a valid council?"

But, ashpenaz, it is good you have moved on to Lutheranism, if only because you have abided by your conscience and no longer have an affinity for what believing Catholics assent to. But in your post, are you suggesting believing Catholics don't believe as much as they ought to or as much as they can regarding your new found faith, the "Augsburg Confession," the "Lutheran church"? This is more than a non-obvious question, especially on a Catholic post.