So you think this verse refers to your church's un-Biblical traditions and you use this verse to justify the other scriptures you posted...
In this verse the traditions which have been taught and the written epistles are identical...They are two in the same...
Think about it...Stand fast, and hold the traditions which ye have been taught.
Do you suppose that if one group read the epistles that they were to stand fast in their beliefs, and another group heard the word of the traditions that were differnt than the written epistle, they were to stand fast in what they heard???
Talking to us in his written epistle Paul is saying that whoever heard the written epistle is to believe that, but if you also, or only heard the unwritten tradition, to believe that as well, or instead???
Sorry...Some churches had copies of the written epistles and others that didn't, heard the epistles spoken word for word from the written source...
And these epistles, spoken or written, became the tradition over the years of what Paul was preaching and teaching...Paul's tradition was his epistles, the bible...Your traditions are not the Bible, but the tradition of men...Paul talks about that as well...