There's a gradient between 'free' and 'held against his will', I'm sure there are plenty of ways Snowden can be discouraged from taking a chance like that.
Yeah, but Russia already looks pretty bad for a variety of other reasons. I don't find this a particularly compelling argument.
They would care you think?
Actually the better question is why would they care about Snowden leaving (or not leaving) Russia? Or why wouldn't Putin let Snowden leave? Snowden is a minor liability for Russia.
I think Snowden is valuable to Putin, he's not just a liability.