Even if correct, he would still be chargeable at the state level in any related state.
The only thing it would protect him against would be the federal murder for hire statute (18 USC 1958).
I doubt the pardon will be considered to cover that, but we'll have to wait to see the text.
The text is now up - https://www.justice.gov/pardon/media/1386096/dl
There is nothing here that would prevent him from being charged with murder for hire, or even other drug crimes.
He was only pardoned as to his existing convictions.