I would never attribute those filigranas to Venini, but that's just me. Salviati and Fratelli Toso are both strong possibilities.
The ruby colored pitcher looks like an iridized piece to me. I don't see anything "scavo" about it. However, it's hard to see in the photo exactly what's going on with the finish. It's a lovely piece, but I'm not sure it's Italian. I'd be interested in seeing more photos.
The little signed decanter is not Scavo. It seems to be what's called "frosted" glass. Scavo is a very rough finish - so rough that you could light a match on it.
Javier is right that there are tons of new scavos out there. I'm not sure most of them are Italian. Cenedese still makes them, but they are signed. As Ivo pointed out, there are lots of replicas of Roman glass that have a Scavo finish.
The early Alfredo Barbini for Cenedese scavos tend to have lots of different (but muted) colors applied to the glass. Their forms are decidely primative, without ornamentation. They are also quite heavy. If the piece offered by the German seller didn't have that curious Seguso sticker, I would have thought it an early Cenedese vase. That such a good reproduction exists worries me more than the cheap Scavos offered all over ebay.
Laura