1) Yes, the canon is not defined in the canon. No book says "I am divinely inspired, and am the final book of which this is true. Here is a list of the previous ones." If the universal church is correct in its acceptance as canonical of those, and only those, writings, then the guidance did of course come from elsewhere.
2) Yes, I am trusting that the church, guided by the Holy Spirit, was correct in the compilation it made.
3) The "other understandings" were not included in either the agreed canon or the ecumenical creeds - though I am aware that the matter of prayer for the dead would be validated if one accepted the Apocrypha as canonical.
Here is where your inconsistency lies. You are basically saying that you do not trust the Church to decide anything (or anything that you disagree with using your Sola Scriptura epistemology) except the Canon of the New Testament. (You seem to accept the Creeds only because you agree with them based on your interpretation of Scripture). The Canon is obviously not found in Scripture, you concede, so we cannot rely on Sola Scriptura to define it. The Church had to decide from amongst literally hundreds of documents, some of which are found herehttp://www.earlychristianwritings.com, what was considered Scripture. Yet, you trust that the Church and its salient Fathers in the first three centuries such as St. Athanasius were guided by the Holy Spirit. So, unless you question the Canon, you are implicitly trusting the Church Fathers. You concede this in you second point.
Yet that very Church and particularly those Fathers such as St. Athanasius clearly espoused a theology and ecclesiology that was radically different from the Baptist faith. How can you trust these Fathers, whose Christian faith you have to conclude was clearly in error in such matters as the Real Presence in the Eucharist, baptismal regeneration and apostolic succession, to correctly be guided by the Holy Spirit in their selection of the Canon?
Don't you think that the theology of the Fathers, which you evidently believe was in error in its consensus (eg they essentially all believed in the Real Presence and an episcopal ecclesiology) could have influenced their very selection of the Canon? Perhaps they selected a Canon that supported their erroneous theology.
If the Father's final selection of the Canon was protected from error by the Holy Spirit, why not their understanding of that Canon? How can you say that the Fathers correctly identified orthodoxy in the selection of the Canon, when you do not believe they were orthodox? Clearly they did not find any fundamental contradictions between their orthodoxy and the Canon they selected, since their understanding of orthodoxy was the filter they used to select the Canon. Isn't it thus rather incomprehensible to assert, as you are doing, that their filter was in error--ie their understanding of true, Apostolic Christianity--yet they still managed to select the right orthodox Canon?
Can you identify any early Christian whose theology you agree with entirely or even substantially who also espoused the final NT Canon?
It would seem those such as yourself whose embrace Sola Scriptura can only really be consistent by rejecting a closed Canon; all other alternatives require you to submit to the judgements of a Church which you believe was in error. Martin Luther did this partially, though this alternative is also fraught with uncomfortable implications.