His FB likes seem to continue to increase every day at a static rate - has he got some kind of auto-like generator on FB as he does with Twitter?
I think that's pretty normal behaviour for a Facebook page with 10s of thousands of 'likes' (real or not). It will grow gradually and organically.
If we'd have been watching it when he bought the fake likes, we would have seen very large jumps. He gained his first 12,000 likes in 14 days (857 per day), which is vastly higher rate of growth compared to now.