How would using an a'dam have helped? It would not have contained Semirhage any better than the shield did. Shaidar Haran would just have removed it. Or Elza for that matter.

Neither do I see torture having helped. It was strongly suggested that physical pain will work poorly on Semirhage. And even if she had broken that way, upon being released she would still have been after revenge. I doubt very much any technique would have worked so well that she would have stayed in the cell after SH visited.

Executing her instantly would have worked ofcourse, but trying to extract information from her seems like a perfectly rational thing. What if she knows something that is the difference between victory and defeat is probably what Rand&Co thought and it is a reasonable thing to think. The wealth of information in both channeling knowledge and shadow secrets they could have potentially received from Semirhage is immense.

So really, I don't really see what it is that you call foolishness here? Trying to extract vital information from an enemy prisoner is foolishness? That makes no sense at all. Yes it turned out badly but thats looking at it in hindsight.

If it was written in the book that Semirhage was not rescued and Cadsuane was able to interrogate all the shadow secrets from her, and someone suggested that they should have just killed her instead, would you have agreed? I doubt it.

As for his survival, Rand was not about to die. Min and the rest of the world were. Rand would probably have outlived nearly everyone, albeit as a prisoner. I expect the DO would have wanted him to be there to witness it when he broke free afterall.