Adding this cause I finally managed to trick steam into thinking we had updated, thamks to all the people who tried this an posted their results, I had to try two different things from two different authors so thanks to both of them. Here is what I did:
Inside the appmanifest_377160.acf change this following lines: (Please make sure to do this while steam is CLOSED, not just closed windows, It must not be running on your machine at all at the moment)
1- "StateFlags" (mine was the 5th line) I changed it from "6" to "4"
2-A little further down you´ll find 4 lines that I also changed
"BytesToDownload" changed its value to "0"
"BytesDownloaded" also changed value to "0"
"BytesToStage" also set it to "0"
"BytesStaged" yes, also set it to "0"
3-Save your file and set it to Read Only again
Now when you open Steam it should show the game as updated with the green play button.
I did this and my game works, but just keep in mind that I always launch it through FO4SE