Radical Attack of NaCN?

I saw a journal of a tertiary halogenated carbon reacting with NaCN in DMSO under UV.

So I know that it was a radical attack, but how would a radical attack an anion?

Also, the journal reported a very high yield for this reaction(73%). I had the understanding that radical reactions are very messy. Why doesn't the radical pluck a hydrogen from DMSO?

Lastly, could a radical attack CO2 to form a carboxy group on the tertiary carbon? Or would it attack the Oxygen's instead?

Thanks