In ` 向谁说`, does `向` play the same role / have the same meaning as `对`?
'誰' in &quot;誰說傷痛?&quot; is equal to the pronoun &quot;who&quot; in English.
誰 is the Subject, 說 is the Verb and 傷痛 is the Object. (It is an SVO sentence)
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'誰' in &quot;傷痛向誰說?&quot; is part of a complement introduced by 向, so it can be translated as the pronoun &quot;whom&quot; in English.
The sentence follows the [topic + comment] structure: 傷痛 is the topic,  向誰說 is the comment:

Topic: 傷痛 = pain


Comment: 向誰說 = whom I should say to

The comment itself is an SVO sentence with the subject omitted
You can have a different comment, e.g. 傷痛(topic) + 我受不了 (comment)

In  向谁说, does 向 play the same role / have the same meaning as 对?

說傷痛 = say pain
[SVO] (向谁)说傷痛 = (to whom) I say pain?
[topic + comment] - 傷痛(向谁)说 = pain, I say (to whom)?
向 sounds more proactive and 对 sounds more interactive

And is 傷痛說向誰 wrong?

傷痛說向誰 is wrong. It is an SVO sentence, the object 傷痛 should not be placed before the verb 說