@Belthazar to the rescue!
That sounds exactly like what we should be doing, indeed!
For your example:
The main point is, as usual, at the end:
最初から信じてなどいなかった I didn’t believe it from the beginning.
Now, there are a few subordinate clauses:
サンタクロースをいつまで信じていたなんてことは About the question “until when did you believe in Santa Claus?”
たわもない世間話にもならないくらいのどうでもいいような話だが、-> 世間話 is small talks, タワもない話 is a story no one cares about (combine both: small talks no one cares about). にもならない doesn’t even become. → “this is a topic so boring that it can’t even reach the status of small talk no one cares about, BUT”
それでも even like that
俺がいつまで until when did I
サンタなどとういう想像上の赤服じーさんを in Santa Claus or whatever, the way we imagine him, that is, an old guy clad in red cloths
信じていたか believed?
というと if we talk about
→ if we still want to ask until when I believed in Santa Claus as an old guy clad in red cloths,
これは確信を持って言えるが最初から信じてなどいなかった。I can say with confidence I haven’t believed in him since the very start.
My break down is probably messy as I was distracted by real life while trying to race @QuackingShoe. I guess I lost on all fronts. Well, I tried.