Who says Worf knows any means of seeing through a breen suit? That Worf - and the federation - has any clue as to how a breen looks like?
But that one can see a breen without a suit is a fact; and just because Worf/the federation don't know when or how to do that doesn't mean someone else didn't figure it out - in urban legend, at least.
As for breen prisoners - they may comit seppuku, letting their suits kill them, rather than revealing details about their species; and their suits kill them when confronted with a scanner that can see through them.
And none of the prisoners the dominion, the cardassians or Kira had feared death enough to talk.
As for breen having no blood, having teen pregnancies:
1. It's obvious the writers changed their mind about the breen in late DS9; why do you keep acting as if someone contested this, Timo?
2. Such remarks can be easily explained by disinformation spread by the breen in order to avoid DNA tests, etc.