Oh wait.... i looked closely at original post.
try this ..you have already copied what you think are valid backups quote " I foud .bd-backups in steamcloud for 20th and 19th february (160mb) and im sure its actual version of my world, "

so
1- copy them somewhere safe.not in valheim structure. ie desktop
2- now start game use normal character.
3- in worlds section, "copy to local" the latest file (dont worry we using it as a placeholder) take note of its name exactly! (important)
4- once done click "back" then "back" until you get to option the quit game
5- Quit game
6- disable steam cloud for valheim
7- start valheim use normal character
8- use latest local save (from step 3-)continue to just make sure game loads starts correctly.
9- when game starts correctly . Quit game ..save if you like
10- OPEN TWO file explorers lets think of them as a) and b)
11- in a)-goto "C:\Users\"UserName"\AppData\LocalLow\IronGate\Valheim\worlds_local"
12- rename the .dbf AND .fwl files with .old so they look like this im using my f
"original filename.dbf.old" and "original filename.fwl.old"
13- in b) goto desktop (or wherever you saved steam cloud files) COPY...do not move..COPY the dbf file
14-PASTE it into a)
15- rename your PASTE'd dbf file the same as the tested working .dbf without the added .dbf.old or the .fwl.old
16- Cross your finger or whatever is local custom...
17-Restart valheim.. and let US know how you go!!