If it was up to me, I would suggest that they should put him in a Russian prison or one of those South-American prisons where the inmates have their own cesspoolsociety with the side of daily murders. Or some bad US prison where they will drill his asshole so wide that its size will be equivalent of a moons crater.
He's not even regretting what he has done. He's just like "I got caught, tough shit, now I demand that u take proper care of me forever". His livingconditions are quite good from what ive read. The lesson here is: if you didnt get that luxury cell you wanted when you got to prison, its quite oblivious you didnt murder enough people to earn it.