yes you have to apply every update until it matches your MaNGOS revision, im wondering how you find out revision numbers also, as they are not posted anywhere and I used GIT to get the release.
As for the UDB .sql file, you dont need to use a text editor, right click your mangos database and go to import in the menu, then click "Restore from SQL Dump" when the window comes up you click the little "..." button and browse for your UDB core .sql file and click execute. I'm hoping this helps you as im not sure what you mean about placing it in a text editor, pasting the contents from the core file into the query box is the same as importing from an sql dump.
I'm also having the "Perhaps sql updates are missing?" error when I run mangosd, even though I updated everything like the guide said, then again I dont even know what revision I'm using cuz I cant find it posted anywhere lol, strangeness...
Edit: I just looked at UDB forum and apparently they haven't updated anything in months, soooo I guess I just cant use mangos til they update... which sux. Either wait or go back to an older server core (I think im going to wait cuz I don't want to have two installs of wow on my computer just to use an old/supported core and db)... wondering why UDB is so far behind mangos team lol