I still think we have to be politic within the Camarilla, rather than turning to the Sabbat to solve our problems. Right now we're quite possibly facing the Final Death. There may not even be a raid in the works, but rather a trap set by the Prince and du Marchais to dispose of our ventrue who they will, I presume, know is antagonistic to their goals.
The raid could just be a ruse to get us out there and to get us killed, we don't know that yet. If we alert the Sabbat to a non-existant raid which causes them, especially their Spymaster who has it in for us, to lose face, they'll come after us with more firepower in the future. If we play along with du Marchais for the moment we can salvage something or at the very least dodge the sunrise for another night while we make our plans.
Dubrik will likely just hang us out to dry. If he's any kind of spymaster, he'll know that something is brewing with the London camarilla and will know that we're either in for the final death or that there is a raid coming and have the necessary precautions in place.
We have to be savvy and sometimes savvy means bowing your head and eating the shit people shovel for you until they become complacent enough to forget about the dagger in your hand. du Marchais thinks he's got us where he wants us- if he cooked up the Sabbat raid (just like we had the option to do when we first heard about the kidnapping) out of desperation, then we have what we need to ensure the whole thing backfires.
Edit- I didn't address the vase, apologies. The vase is a bargaining chip, but it only has personal power over Dubrik who wants it, or our head. Right now we're not tussling with Dubrik, we're tussling with du Marchais and Kirkbeck. Dubrik likely won't negotiate, but rather just send in more shovelheads hoping to destabilise the London Camarilla and its ineffectual Prince even more. We might even be killed in the raid, which means he can get his vase or satisfaction.