You say
Sources and other evidence determine which traditions are to be believed and which are not
There are no sources and other evidence, just the tradition itself - that's the point I'm trying to make. Additionally, there are so many conflicting traditions about the death of various apostles without any supporting evidence that you'd be hard pressed to determine which tradition to take as the definitive one.
If you think hearsay is evidence, try telling that to a judge. Stories change in the telling, bits are misunderstood, bits are embellished, bits are mistranslated, whatever, and to determine the actual story can be well nigh impossible. Can you give me one solid bit of evidence that the apostles ALL died martyrs deaths alone and could have avoided said death by recanting? Not tradition, not hearsay, not "In the opinion of Dr Scott", just one solid, verifiable piece of evidence which is irrefutable.