1. "and" vs "with"
When I read the Japanese, the と in ゴーストとダンブルドアの白髪だけ means "and".
This is because 同じようにキラキラ輝いている in English can be read as "similarly glitter shining" in a literal sense. Also the が, which marks ゴーストとダンブルドアの白髪だけ as what is "similarly glitter shining", gives backing to the と being intended as "and".
That being said, there might be some ambiguity where と could be treated as "with" instead. However, I feel like the Japanese's sentence composition or structure would be different in order for the "with" to be more apparent for English.
2. Use of だけ
When it comes to だけ, it simply means "only; just; nothing but; etc" here. ゴーストとダンブルドアの白髪だけ can literally be read as "the ghost(s) and only Dumbledore's silver hair".
To me this means that there is nothing happening in the hall except the glowing of the ghosts and Dumbledore's hair. That's not what the original text says. In fact I'm struggling to see how this sentence reproduces the meaning of the original at all.
In my opinion, translations can be dangerous and often a trap because they are interpretations at the end of the day. Let me try and illustrate this:
Original English from Harry Potter:
Dumbledore's silver hair was the only thing in the whole hall that shone as brightly as the ghosts.
My translation of the Japanese:
Within the hall, the ghosts and only Dumbledore's silver hair glittered similarly.
Your "and" version:
Only the ghosts and Dumbledore's silver hair are shining in the same way [within the hall].
When looking at our interpretations, they have the same meaning and are just worded differently. Additionally, I agree that you could also say our interpretations could mean "there is nothing happening in the hall except the glowing of the ghosts and Dumbledore's hair" even though it's not explicitly stated, which is all thanks to the number of ways the Japanese can be interpreted into English.
And that is the key thing to realize here, we are both interpreting the Japanese, which is an interpretation of the original English.
This leaves a lot of room for things to get lost in translation. And why "that's not what the original text says. In fact I'm struggling to see how this sentence reproduces the meaning of the original at all." becomes very apparent and getting back to the original meaning from the Japanese is impossible in this case.