which strongly suggests your DH was driving quite slowly
no, he has admitted driving at 30mph, which is likely to be considered too fast if its taken to court, 30mph is the MAXIMUM for optimum conditions, not in the dark, in the rain, etc.
This is no scam, the pedestrian had a good chance of being killed.
The driver needed to have called the police immediately, or gone straight to a police station, if he felt at risk.
He is now in a position of having to explain why he didn't, and the most obvious assumption is going to be it was to avoid being breathalyzed, particularly s the story bout needing milk at 1 am is odd, to say the least.
The pedestrian could be badly hurt, fractured skull, broken neck, etc all things that may not be immediately apparent, and should have been checked for, BEFORE he moved.
The driver was responsible for reporting it immediately, calling an ambulance and police, and making it very clear he wanted the pedestrian to stay still and be checked.