Emmy - I agree 1000% with everything that's been said. He's an abusive asshat who is exploiting this situation in order to continue abusing you in a way he knows will strike right at your heart. F*** him. Plus - how freaking illogical to think that this would have ANY impact whatsoever on his DUI charges. Asshat is really too mild a term.
And FWIW I'm not ashamed to admit I DID THIS EXACT SAME THING with DD when she was a bit younger than your DS. It really DOES happen to people, the firefighters were not just giving you lip service. Luckily I was able to call AAA, explain the urgency & they sent a service car pronto. The whole event was over & done with in minutes, but it was HOURS before my nerves & guilt settled down.... DD was pretty unaffected for the most part.
You are a GREAT MOM, don't buy into his quacking!