No, what you have is an ovalform bariton or a tenorhorn, depending on what the bell shape and bore size are. These existed as military band instruments well before Wagner Tubas were invented. German-style Bariton is roughly the equivalent of a euphonium, just with a different shape and usually with rotary valves. This is still used for euphonium parts in German and other Eastern European concert bands. Tenorhorn is similar to the british-style baritone -- but again, usually with rotary valves and in the oval shape, but not quite as small. The overall sound and bore profile is closer to a smallish american-style baritone horn than anything else. These are mostly useful these days in German and Austrian folk music.
Tuben is the plural of tuba. It is not uncommon to see a section of Wagner tubas referred to as just "tuben", whereas an actual tuba would be "tuba" or "basstuba" or "kontrabasstuba." But I am not aware of bariton and tenorhorn being referred to in that way.
Wagner tubas were invented in the early 1860s. They aren't really members of the tuba family at all, but a hybrid between a horn and a saxhorn. They come in two sizes -- Bb which is the same length as a baritone or euphonium, or F which is the same length as an F tuba or a single F horn. There are a few manufacturers who have made double wagner tubas, but this is not ideal as it ignores the inherant tonal differences in the two instruments. They are almost always used by composers as a group of four, two tenors and two basses.
Yes, it's possible that your issue is a problem with the spring or linkage rather than the rotor itself. Does your instrument have clocksprings? These are leaf springs that are wound into a coil and are usually in a cylindrical container attached to the valve paddle. These are notoriously difficult to adjust and you may want to try to substitute in a more modern linkage and springs.