Assuming he loves and cares about his child, which you seems convinced of:
Use scare tactics, definitely. To the full extent, whatever it takes to inform him fully on the risk he took. The documentation is widespread, this is incontrovertible stuff. When he is presented with hard evidence, then he will surely be scared straight. Give him evidence from sources that aren't you. Give him a leaflet to read, don't read it to him. Because he can't feel a leaflet may be overmothering or cosseting the baby to his exclusion, and if he feels you have any history of doing these things, whether rightly or wrongly, then it is very easy and almost natural to react to this by lumping this situation in with those other instances, no matter how authoritively and convincingly you speak on the subject of SIDS. Because the alternative, the horrible truth, that he endangered his precious child unknowingly, is too unbearable to face up to.
But once he's absolutely got the message and tells you he will never do this again (which he must, and will) don't be too mad at him. Be vigilant for other urgent blind spots there may be in his parenting (as subtly as you can do so whilst fully satisfying your concerns). But don't be too mad once the danger is gone. While it is incontrovertible that SIDS was possible from what he did, it is not intuitive to a person lying peacefully with their baby on the sofa feeling like cuddling up for a nap. He didn't think he was putting your DC at risk. Be mad a tiny little bit for his thinking you were exaggerating the dangers or over worrying. And also at that blokey self-assurance that means he must never admit he doesn't know what he's doing, (irritating at refusing-to-ask-for-directions level, potentially lethal here). But let these angers be ultimately overwhelmed by the knowledge his actions, however horrifying, were not in the slightest bit malicious, but came from the same love you have for your DC.
Fathers can sometimes feel that the mother is overprotective of her child and institutes all these needless strict regulations and regimes for them which prevent him from bonding with the child and make him feel like a bit of a nuisance. He may resent the mother for portraying him as a danger to his child, when he doesn't believe he could ever possibly do anything to hurt something he loves so much. Your DH may be feeling left out and hurt in a way he can't quite articulate, and this is what is causing his over-defensiveness and selfishness. Be sympathetic to this, reassure him of his status. Don't apologise for his feeling like this (unless you are a generally overprotective mother, I've no way of knowing, and while your post does nothing to imply you are like that, it can happen)
Share with him your own fears for ever harming your baby through a careless, exhausted moment. Don't make him feel like you think you have all the answers and are training him as an incompetent subordinate, but instead are just sharing a piece of vital information as two people in love on a hazardous journey will naturally together. Praise him on his strengths as a father. Ask him to keep a watchful eye on your alertness if ever you seem drowsy when with the baby on the sofa. Remind him that no parent can ever really know what they're doing, and co-operating and helping each other is vital to your success. Tell him you need him, as a loving partner and responsible father but also as somebody to be scared with.
If I am excusing him partly "because he's a dad", then it's because it's entirely natural and unavoidable that the bloke is going to feel like a bit of a third wheel to some kind of deep bond between a baby and the woman who gestates, and as someone else said, it's something that mums are more likely to know about in most instances due to the extra exposure to warning posters etc.