You would only have 1 klaw if you put a warboss with snikrot. As snikrot counts as a nob and has no option for one
I found the latest one because I knew they changed their mindsFun thing I found, in the Adepticon INATFAQ (the FAQ used by Adepticon, pretty much the biggest warhammer tournament, and generally pretty widely accepted in the tournament scene, specifies that ICs joining a painboy's unit do get FNP. (In the Ork section)
Oh, it also specifies that no one can join Snikrot's unit and benefit from Ambush.