You can't just change ops around willy-nilly.
I took over because I wrote the RNG and to be fair the OP shouldn't have posted it because he knew none of the theory behind it so I came in to answer and clarify things for some of the posters.
As for the period as you said it is 2^64 - 1 (Maximal) which is why I chose these numbers. As for the statistical properties, I didn't realise that different choices in numbers could effect it. I will have to read up and better understand all these properties. As for now, I will change the values to your last suggested ones and have the OP correct it in the code.
Edit: I'm not having a go at the OP there he is trying to do the right thing by the community and provide you guys with some working code =)