^ Why would the GQ Dominion be as vulnerable as the AQ powers? They just spent 2 years not fighting a war on home ground. Their loss might see a rise of rebellious activity inside their borders due to a chink in their aura of invincibility, but with the return of their AQ forces the GQ Dominion would be stronger, not weaker
The novels are the only things that give a definitive statement on what happened to the Female Changeling and they state she was imprisoned in a special facility in the Federation after the war. I think they also say the Dominion fleet was allowed to return to the GQ.
As for the wormhole I'm not sure what the books say about how it operated post-SoA. Whether the Prophets had locked it down from the GQ or not. Even if they had the Federation would be sensible to put up a new minefield immediately rather than depend on the whims of the wormhole aliens.