1 is somewhat addressed by the continuation of the article.
2 I have no clue what you are talking about
3 What exactly is the signifcance of some strange happening of the sun? The phenomenon did not tell them anything all it was just some sort of event at most.
1. I said it downplays it. It's really significant especially because of..
2. We're told we're not allowed to question chazal, gedolim, etc., and it's been that way for eons. If their gedolim told them that 600,000 heard/saw it, it would be accepted without question; not like in the scenarios he describes. Additionally, they saw their leaders as having a direct connection to HaShem.
3. It was allegedly a predicted miracle. That's like asking what's the significance of some lightning and thunder at Har Sinai.
"Before the astonished eyes of the crowd, whose aspect was biblical as they stood bare-headed, eagerly searching the sky, the sun trembled, made sudden incredible movements outside all cosmic laws..."
That even sounds like something that could have been seen at Har Sinai.