I would guess that Snape was asked a number of other questions as well since you stated they had about 6 hours of time before a reaction to the overdose set in. Normal interrogation procedure is to find out what the subject had for breakfast the year before if possible.
Enjoyed it.
Author's response
Heya Pointer.
If I went all out, that chapter would have been about thirty thousand words. I may touch on the interrogation once mere, for background, specifically when Lucy goes down, but for the rest, let us assume that whatever they need, Snape will have confessed.
Glad you enjoyed.
Alorkin