Please pick up a basic introductory textbook to the history of the Slavic languages. Your understanding of the relationship between them is very mistaken. If you want to read in Russian, I can recommend К. А. Войлова’s
Старославянский язык, which describes not only what Old Church Slavonic is, but also the family tree of the Slavic languages in general and how Russian, Belarusian and Ukrainian are not a direct descendant of Old Church Slavonic. If you want to read in English, Alexander Schenker’s
The Dawn of Slavic covers much of the same ground in an accessible fashion.
> Russians do not have common ancestry in Proto-Slavic, because ancestors of Rus people in majority did not even speak Slavic languages
When historical-comparative linguists say "common ancestry", they mean common linguistic ancestry, not the genetic ancestry of the Slavic languages' speakers.
> All the survived early written texts of Rus are in Old Church Slavonic
This is not the case. The Novgorod birchbark letters that were excavated over the 20th century attest some early East Slavic, noticeably different from the Old Church Slavonic language that was borrowed into Russia/Belarus/Ukraine around the same time as a literary standard after the christianization of the region.
> You and me are not going to decide the classification of languages, that are based purely on geographic distribution
The distinctions "West Slavic", "East Slavic" and "South Slavic" aren't actually based on the geographic distribution. Rather, they are based on the isoglosses that set the Slavic languages apart from one another. The terms "East/West/South" for the basic post-Proto-Slavic isoglosses are used only because those isoglosses map roughly with those cardinal directions. Again, this is something covered in any basic textbook.
> Бере-менна can not even be explained by Slavic language, or Proto... Baltic, but it can be explained by Swedish language, where bear-men was clear purpose of Rus women.
No, беременна is a native Slavic word and not a Swedish borrowing; it goes back to the same root as беру. If it looks similar to a Swedish word, this is only because the Slavic languages and the Germanic languages both inherited the same Proto-Indo-European word. A detailed etymology for the Russian word can be found in Vasmer under the headword *беремя*.