It certainly would have kept the leaks in the news cycle for much longer and not delegitimized his motives. It’s anyone’s guess whether that would have had any real effect on policy.
If he stayed in the US he would've been thrown into a dark, black hole for all eternity to be tortured by the same types of sociopaths in the US gov't who committed atrocities like Abu Ghraib. I'll take being a Russian "asset" over the wrath of the US intelligence services any day of the week.
I doubt he could have been disappeared after all of the attention. Chelsea Manning wasn’t disappeared despite causing a similar black eye for the US government.
I’d argue he is more physical danger now being in a mafia state near an active war zone.
That said, I wouldn’t come back and subject myself the whims of this administration.
He made it real easy for himself to be written off as a Russian asset.