Really?
The replays show clearly that the Paraguayan player did catch the back of Villa's legs. Whether he dived or not doesn't change the fact that the contact caused him to lose his balance. I don't even think anyone would complain if the ref showed a red card there, he was 1 to 1 with the keeper.
In the 2nd pen, Villa got the rebound ball when Fabregas went to the ground, so the ref could've given the advantage to Villa, but it happened in a matter of seconds, I think the ref had no idea what's going on