Hope you've got the barrels opened by now?

Regarding your second question, about pivot mounts, the German brand Recknagel usually two piece bases, rings and mounts for chapuis. They're rather expensive but tell me what's not expensive when it comes to double rifles. It might perhaps be possible to fit in weaver style bases on your rifle as well, and use ordinary QD rings as leupold qrw, but you'll probably end up with a price that matches the original Recknagel pivot mount as the job probably needs a skilled gunsmith. It will however certainly look uglier and not be as firm as a pivot mount. I'd say, go for a pivot mount, it's the best choice and will last as long as the rifle. If you don't have the money now, use the iron sight until you can afford a good mount.